### Install python-fints with pip3

Source: https://python-fints.readthedocs.io/en/latest/_sources/quickstart.rst.txt

Installs the python-fints library using pip3. Run this in a terminal to begin using the FinTS client.

```console
$ pip3 install fints
```

--------------------------------

### Full example: get transactions with TAN handling

Source: https://python-fints.readthedocs.io/en/latest/_sources/tans.rst.txt

Full example for getting transactions when a TAN is required. If a TAN is required, result is a NeedTANResponse; otherwise it holds transactions directly. Uses minimal_interactive_cli_bootstrap and terminal_flicker_unix for TAN entry.

```python
import datetime
from fints.utils import minimal_interactive_cli_bootstrap
from fints.client import FinTS3PinTanClient, NeedTANResponse
from fints.hhd.flicker import terminal_flicker_unix

from credentials import blz, username, password, hbci_backend

product_id = "CHANGE_ME"

def ask_for_tan(f, response):
    print("A TAN is required")
    print(response.challenge)
    if getattr(response, 'challenge_hhduc', None):
        try:
            terminal_flicker_unix(response.challenge_hhduc)
        except KeyboardInterrupt:
            pass
    if response.decoupled:
        tan = input('Please press enter after confirming the transaction in your app:')
    else:
        tan = input('Please enter TAN:')
    return f.send_tan(response, tan)

client = FinTS3PinTanClient(blz,
                            username,
                            password,
                            hbci_backend,
                            product_id=product_id)
minimal_interactive_cli_bootstrap(client)
with client:
    while isinstance(client.init_tan_response, NeedTANResponse):
        client.init_tan_response = ask_for_tan(client, client.init_tan_response)

    accounts = client.get_sepa_accounts()
    for account in accounts:
        print(f"Doing {account.iban}")
        result = client.get_transactions(account,
                                         start_date=datetime.datetime.now() - datetime.timedelta(days=100),
                                         end_date=datetime.datetime.now())
        if isinstance(result, NeedTANResponse):
            result = ask_for_tan(client, result)
        else:
            print("No TAN is required")
        print(f"Got {len(result)} transactions for {account.iban}")
```

--------------------------------

### Initialize FinTS3PinTanClient

Source: https://python-fints.readthedocs.io/en/latest/quickstart.html

Initializes a FinTS3PinTanClient with the bank's BLZ, login name, PIN, and HBCI endpoint. Logging in with a signature file or chip card is not supported. Requires the fints library to be installed.

```python
import logging
from datetime import date
import getpass
from fints.client import FinTS3PinTanClient

logging.basicConfig(level=logging.DEBUG)
f = FinTS3PinTanClient(
    '123456789',  # Your bank's BLZ
    'myusername',  # Your login name
    getpass.getpass('PIN:'),  # Your banking PIN
    'https://hbci-pintan.gad.de/cgi-bin/hbciservlet',  # Your bank's HBCI endpoint
)

```

--------------------------------

### Choose TAN method with minimal_interactive_cli_bootstrap

Source: https://python-fints.readthedocs.io/en/latest/_sources/quickstart.rst.txt

Launches a minimal interactive command-line utility to help choose a TAN method after client initialization. Useful for quick starts to handle PSD2 TAN challenges.

```python
from fints.utils import minimal_interactive_cli_bootstrap
minimal_interactive_cli_bootstrap(f)
```

--------------------------------

### Full example: interactive SEPA transfer with TAN and VOP handling

Source: https://python-fints.readthedocs.io/en/latest/transfers.html

Shows a complete interactive SEPA transfer flow with TAN and VOP handling. It initializes the client, handles the initial TAN challenge, performs a simple transfer, and then loops through NeedTANResponse and NeedVOPResponse responses, prompting for TAN or confirming payee verification before printing the final status and responses.

```python
client = FinTS3PinTanClient(...)
minimal_interactive_cli_bootstrap(client)

with client:
    if client.init_tan_response:
        print("A TAN is required", client.init_tan_response.challenge)

        if getattr(client.init_tan_response, 'challenge_hhduc', None):
            try:
                terminal_flicker_unix(client.init_tan_response.challenge_hhduc)
            except KeyboardInterrupt:
                pass

        tan = input('Please enter TAN:')
        client.send_tan(client.init_tan_response, tan)

    res = client.simple_sepa_transfer(
        account=accounts[0],
        iban='DE12345',
        bic='BIC12345',
        amount=Decimal('7.00'),
        recipient_name='Foo',
        account_name='Test',
        reason='Birthday gift',
        endtoend_id='NOTPROVIDED',
    )

    while isinstance(res, NeedTANResponse | NeedVOPResponse):
        if isinstance(res, NeedTANResponse):
            print("A TAN is required", res.challenge)

            if getattr(res, 'challenge_hhduc', None):
                try:
                    terminal_flicker_unix(res.challenge_hhduc)
                except KeyboardInterrupt:
                    pass

            if result.decoupled:
                tan = input('Please press enter after confirming the transaction in your app:')
            else:
                tan = input('Please enter TAN:')
            res = client.send_tan(res, tan)
        elif isinstance(res, NeedVOPResponse):
            if res.vop_result.vop_single_result.result == "RCVC":
                print("Payee name is an exact match")
                if res.vop_result.vop_single_result.other_identification:
                    print("Other info retrieved by bank:", res.vop_result.vop_single_result.other_identification)
            elif res.vop_result.vop_single_result.result == "RVMC":
                print("Payee name is a close match")
                print("Name retrieved by bank:", res.vop_result.vop_single_result.close_match_name)
                if res.vop_result.vop_single_result.other_identification:
                    print("Other info retrieved by bank:", res.vop_result.vop_single_result.other_identification)
            elif res.vop_result.vop_single_result.result == "RVNM":
                print("Payee name does not match match")
            elif res.vop_result.vop_single_result.result == "RVNA":
                print("Payee name could not be verified")
                print("Reason:", res.vop_result.vop_single_result.na_reason)
            elif res.vop_result.vop_single_result.result == "PDNG":
                print("Payee name could not be verified (pending state, can't be handled by this library)")
            print("Do you want to continue? Your bank will not be liable if the money ends up in the wrong place.")
            input('Please press enter to confirm or Ctrl+C to cancel')
            res = client.approve_vop_response(res)

    print(res.status)
    print(res.responses)

```

--------------------------------

### Get TAN media with Postbank workaround

Source: https://python-fints.readthedocs.io/en/latest/_modules/fints/client.html

Retrieves TAN media information. For Postbank (URL https://hbci.postbank.de/banking/hbci.do) it uses a lazy-init dialog and the init method; otherwise it uses a regular dialog and the send method.

```python
    def get_tan_media(self, media_type = TANMediaType2.ALL, media_class = TANMediaClass4.ALL):
        """Get information about TAN lists/generators.

        Returns tuple of fints.formals.TANUsageOption and a list of fints.formals.TANMedia4 or fints.formals.TANMedia5 objects."""
        if self.connection.url == 'https://hbci.postbank.de/banking/hbci.do':
            # see https://github.com/raphaelm/python-fints/issues/101#issuecomment-572486099
            context = self._new_dialog(lazy_init=True)
            method = lambda dialog: dialog.init
        else:
            context = self._get_dialog()
            method = lambda dialog: dialog.send
```

--------------------------------

### Diagnostic script for FinTS3PinTanClient with TAN and VOP handling

Source: https://python-fints.readthedocs.io/en/latest/_sources/trouble.rst.txt

Run this script to test the affected feature of the library. Replace the placeholder arguments (BLZ, USER, PIN, ENDPOINT, product_id) with your bank's parameters and credentials. Do not modify the rest of the script. If it fails, report an issue with the bank name and failing operations; if it works, include full working example code in your issue. The script handles TAN challenges and VOP (Verification of Payee) responses.

```python
import datetime
import getpass
import logging
import sys
from decimal import Decimal

from fints.client import FinTS3PinTanClient, NeedTANResponse, FinTSUnsupportedOperation
from fints.hhd.flicker import terminal_flicker_unix
from fints.utils import minimal_interactive_cli_bootstrap

logging.basicConfig(level=logging.DEBUG)

client_args = (
    'REPLACEME',  # BLZ
    'REPLACEME',  # USER
    getpass.getpass('PIN: '),
    'REPLACEME'  # ENDPOINT
)
product_id = 'REPLACEME'

f = FinTS3PinTanClient(*client_args, product_id=product_id)
minimal_interactive_cli_bootstrap(f)


def ask_for_tan(response):
    print("A TAN is required")
    print(response.challenge)
    if getattr(response, 'challenge_hhduc', None):
        try:
            terminal_flicker_unix(response.challenge_hhduc)
        except KeyboardInterrupt:
            pass
    if response.decoupled:
        tan = input('Please press enter after confirming the transaction in your app:')
    else:
        tan = input('Please enter TAN:')
    return f.send_tan(response, tan)


def ask_for_vop(response: NeedVOPResponse):
    if response.vop_result.vop_single_result.result == "RVMC":
        print("Payee name is a close match")
        print("Name retrieved by bank:", response.vop_result.vop_single_result.close_match_name)
        if response.vop_result.vop_single_result.other_identification:
            print("Other info retrieved by bank:", response.vop_result.vop_single_result.other_identification)
    elif response.vop_result.vop_single_result.result == "RVNM":
        print("Payee name does not match match")
    elif response.vop_result.vop_single_result.result == "RVNA":
        print("Payee name could not be verified")
        print("Reason:", response.vop_result.vop_single_result.na_reason)
    elif response.vop_result.vop_single_result.result == "PDNG":
        print("Payee name could not be verified (pending state, can't be handled by this library)")
    print("Do you want to continue? Your bank will not be liable if the money ends up in the wrong place.")
    input('Please press enter to confirm or Ctrl+C to cancel')
    return f.approve_vop_response(response)


# Open the actual dialog
with f:
    # Since PSD2, a TAN might be needed for dialog initialization. Let's check if there is one required
    while isinstance(f.init_tan_response, NeedTANResponse):
        f.init_tan_response = ask_for_tan(f.init_tan_response)
```

--------------------------------

### FinTS3Segment subclass example output

Source: https://python-fints.readthedocs.io/en/latest/_sources/developer/segments/index.rst.txt

Shows the expected representation of a parsed segment as a nested list, as produced by the FinTS3Segment class. The example is a Python list literal representing a segment header and its fields.

```python
['Segment', 'HNHBK', 3, 0, 1]
```

--------------------------------

### Send SEPA transfer with TAN and VOP handling

Source: https://python-fints.readthedocs.io/en/latest/_sources/transfers.rst.txt

Complete example of sending a SEPA transfer with the FinTS3PinTanClient. It handles an initial TAN challenge, calls simple_sepa_transfer, and loops through NeedTANResponse and NeedVOPResponse responses, prompting for TANs and approving VOP responses as needed. The code uses helper functions minimal_interactive_cli_bootstrap and terminal_flicker_unix that are not defined in this snippet.

```python
client = FinTS3PinTanClient(...)
minimal_interactive_cli_bootstrap(client)

with client:
    if client.init_tan_response:
        print("A TAN is required", client.init_tan_response.challenge)

        if getattr(client.init_tan_response, 'challenge_hhduc', None):
            try:
                terminal_flicker_unix(client.init_tan_response.challenge_hhduc)
            except KeyboardInterrupt:
                pass

        tan = input('Please enter TAN:')
        client.send_tan(client.init_tan_response, tan)

    res = client.simple_sepa_transfer(
        account=accounts[0],
        iban='DE12345',
        bic='BIC12345',
        amount=Decimal('7.00'),
        recipient_name='Foo',
        account_name='Test',
        reason='Birthday gift',
        endtoend_id='NOTPROVIDED',
    )

    while isinstance(res, NeedTANResponse | NeedVOPResponse):
        if isinstance(res, NeedTANResponse):
            print("A TAN is required", res.challenge)

            if getattr(res, 'challenge_hhduc', None):
                try:
                    terminal_flicker_unix(res.challenge_hhduc)
                except KeyboardInterrupt:
                    pass

            if result.decoupled:
                tan = input('Please press enter after confirming the transaction in your app:')
            else:
                tan = input('Please enter TAN:')
            res = client.send_tan(res, tan)
        elif isinstance(res, NeedVOPResponse):
            if res.vop_result.vop_single_result.result == "RCVC":
                print("Payee name is an exact match")
                if res.vop_result.vop_single_result.other_identification:
                    print("Other info retrieved by bank:", res.vop_result.vop_single_result.other_identification)
            elif res.vop_result.vop_single_result.result == "RVMC":
                print("Payee name is a close match")
                print("Name retrieved by bank:", res.vop_result.vop_single_result.close_match_name)
                if res.vop_result.vop_single_result.other_identification:
                    print("Other info retrieved by bank:", res.vop_result.vop_single_result.other_identification)
            elif res.vop_result.vop_single_result.result == "RVNM":
                print("Payee name does not match match")
            elif res.vop_result.vop_single_result.result == "RVNA":
                print("Payee name could not be verified")
                print("Reason:", res.vop_result.vop_single_result.na_reason)
            elif res.vop_result.vop_single_result.result == "PDNG":
                print("Payee name could not be verified (pending state, can't be handled by this library)")
            print("Do you want to continue? Your bank will not be liable if the money ends up in the wrong place.")
            input('Please press enter to confirm or Ctrl+C to cancel')
            res = client.approve_vop_response(res)

    print(res.status)
    print(res.responses)
```

--------------------------------

### Startcode class for HHD start codes

Source: https://python-fints.readthedocs.io/en/latest/_modules/fints/hhd/flicker.html

Startcode class for parsing and rendering HHD start codes. It reads the length and control bytes, supports HHD versions 13 and 14, and adjusts the rendered length when control bytes are present.

```python
class Startcode(DE):
    def __init__(self):
        super().__init__(LDE_LENGTH_DEFAULT)
        self.control_bytes = []

    def parse(self, data):
        self.lde = int(data[:2], 16)
        data = data[2:]

        self.length = bit_sum(self.lde, 5)

        self.version = HHD_VERSION_13
        if self.lde & (1 << BIT_CONTROLBYTE) != 0:
            self.version = HHD_VERSION_14
            for i in range(10):
                cbyte = int(data[:2], 16)
                self.control_bytes.append(cbyte)
                data = data[2:]
                if cbyte & (1 << BIT_CONTROLBYTE) == 0:
                    break

        self.data = data[:self.length]
        return data[self.length:]

    def render_length(self):
        s = super().render_length()
        if self.version == HHD_VERSION_13 or not self.control_bytes:
            return s
        l = int(s, 16) + (1 << BIT_CONTROLBYTE)
        return h(l, 2)
```

--------------------------------

### Initialize FinTS3PinTanClient with credentials and product ID

Source: https://python-fints.readthedocs.io/en/latest/_sources/quickstart.rst.txt

Initializes a FinTS3PinTanClient with your bank's BLZ, username, PIN, and HBCI endpoint. Requires a registered product ID (see DK registration). Placeholder values are shown; replace them with your actual credentials and endpoint. Logging is set to DEBUG for verbosity.

```python
import logging
from datetime import date
import getpass
from fints.client import FinTS3PinTanClient

logging.basicConfig(level=logging.DEBUG)
f = FinTS3PinTanClient(
    '123456789',  # Your bank's BLZ
    'myusername',  # Your login name
    getpass.getpass('PIN:'),  # Your banking PIN
    'https://hbci-pintan.gad.de/cgi-bin/hbciservlet',
    product_id='Your product ID'  # see above
)
```

--------------------------------

### Defining a custom segment class

Source: https://python-fints.readthedocs.io/en/latest/_sources/developer/segments/index.rst.txt

Example of defining a custom segment class using DataElementField.

```APIDOC
## [CLASS] Custom Segment Class Definition

### Description
Shows how to define a custom FinTS segment class by subclassing FinTS3Segment and specifying fields with DataElementField.

### Example
```python
from fints.segments.base import FinTS3Segment
from fints.fields import DataElementField

class HNHBS1(FinTS3Segment):
    message_number = DataElementField(type='num', max_length=4)
```

### Notes
- The class name determines TYPE and VERSION automatically if it consists of uppercase letters followed by digits.
- All type conversion and construction are handled automatically.
```

--------------------------------

### Get current TAN mechanism

Source: https://python-fints.readthedocs.io/en/latest/_modules/fints/client.html

Returns the currently selected TAN mechanism (security function).

```python
    def get_current_tan_mechanism(self):
        return self.selected_security_function
```

--------------------------------

### print_nested output for HNHBS1

Source: https://python-fints.readthedocs.io/en/latest/developer/segments/index.html

Example output of print_nested on an instance of the HNHBS1 segment class. The output is eval()able to reconstruct the object.

```python
fints.segments.HNHBS1(
    header = fints.formals.SegmentHeader('HNHBS', 4, 1),
    message_number = 1,
)

```

--------------------------------

### Open dialog with bank and fetch SEPA accounts

Source: https://python-fints.readthedocs.io/en/latest/_sources/quickstart.rst.txt

Opens a communication dialog with the bank using a context manager. Checks if a TAN is required for initialization本体 and prompts for it, then fetches SEPA accounts. Requires the client from the previous initialization step.

```python
with f:
    # Since PSD2, a TAN might be needed for dialog initialization. Let's check if there is one required
    if f.init_tan_response:
        print("A TAN is required", f.init_tan_response.challenge)
        tan = input('Please enter TAN:')
        f.send_tan(f.init_tan_response, tan)

    # Fetch accounts
    accounts = f.get_sepa_accounts()
```

--------------------------------

### Get available TAN mechanisms

Source: https://python-fints.readthedocs.io/en/latest/_modules/fints/client.html

Returns a dictionary mapping security_function to TwoStepParameters for available TAN mechanisms. Only considers HITANS versions listed in IMPLEMENTED_HKTAN_VERSIONS and filters by allowed_security_functions.

```python
    def get_tan_mechanisms(self):
        """
        Get the available TAN mechanisms.

        Note: Only checks for HITANS versions listed in IMPLEMENTED_HKTAN_VERSIONS.

        :return: Dictionary of security_function: TwoStepParameters objects.
        """

        retval = OrderedDict()

        for version in sorted(IMPLEMENTED_HKTAN_VERSIONS.keys()):
            for seg in self.bpd.find_segments('HITANS', version):
                for parameter in seg.parameter.twostep_parameters:
                    if parameter.security_function in self.allowed_security_functions:
                        retval[parameter.security_function] = parameter

        return retval
```

--------------------------------

### Diagnostic script for FinTS3PinTanClient

Source: https://python-fints.readthedocs.io/en/latest/trouble.html

Run this script to test the affected feature of the library. Replace the placeholders (BLZ, USER, ENDPOINT, product_id) with your bank's parameters and credentials. Do not modify the script otherwise; pasting it into a Jupyter notebook is considered a modification. If the script fails, the issue is likely a compatibility problem with your bank; if it works, the issue is likely in your usage. Ensure no sensitive data (username, PIN, IBAN) is included when reporting.

```python
import datetime
import getpass
import logging
import sys
from decimal import Decimal

from fints.client import FinTS3PinTanClient, NeedTANResponse, FinTSUnsupportedOperation
from fints.hhd.flicker import terminal_flicker_unix
from fints.utils import minimal_interactive_cli_bootstrap

logging.basicConfig(level=logging.DEBUG)

client_args = (
    'REPLACEME',  # BLZ
    'REPLACEME',  # USER
    getpass.getpass('PIN: '),
    'REPLACEME'  # ENDPOINT
)
product_id = 'REPLACEME'

f = FinTS3PinTanClient(*client_args, product_id=product_id)
minimal_interactive_cli_bootstrap(f)


def ask_for_tan(response):
    print("A TAN is required")
    print(response.challenge)
    if getattr(response, 'challenge_hhduc', None):
        try:
            terminal_flicker_unix(response.challenge_hhduc)
        except KeyboardInterrupt:
            pass
    if response.decoupled:
        tan = input('Please press enter after confirming the transaction in your app:')
    else:
        tan = input('Please enter TAN:')
    return f.send_tan(response, tan)


def ask_for_vop(response: NeedVOPResponse):
    if response.vop_result.vop_single_result.result == "RVMC":
        print("Payee name is a close match")
        print("Name retrieved by bank:", response.vop_result.vop_single_result.close_match_name)
        if response.vop_result.vop_single_result.other_identification:
            print("Other info retrieved by bank:", response.vop_result.vop_single_result.other_identification)
    elif response.vop_result.vop_single_result.result == "RVNM":
        print("Payee name does not match match")
    elif response.vop_result.vop_single_result.result == "RVNA":
        print("Payee name could not be verified")
        print("Reason:", response.vop_result.vop_single_result.na_reason)
    elif response.vop_result.vop_single_result.result == "PDNG":
        print("Payee name could not be verified (pending state, can't be handled by this library)")
    print("Do you want to continue? Your bank will not be liable if the money ends up in the wrong place.")
    input('Please press enter to confirm or Ctrl+C to cancel')
    return f.approve_vop_response(response)


# Open the actual dialog
with f:
    # Since PSD2, a TAN might be needed for dialog initialization. Let's check if there is one required
    while isinstance(f.init_tan_response, NeedTANResponse):
        f.init_tan_response = ask_for_tan(f.init_tan_response)

    # Fetch accounts
    accounts = f.get_sepa_accounts()
    while isinstance(accounts, NeedTANResponse):
        accounts = ask_for_tan(accounts)
    if len(accounts) == 1:
        account = accounts[0]
    else:
        print("Multiple accounts available, choose one")
        for i, mm in enumerate(accounts):
            print(i, mm.iban)
        choice = input("Choice: ").strip()
        account = accounts[int(choice)]

    # Test pausing and resuming the dialog
    dialog_data = f.pause_dialog()

client_data = f.deconstruct(including_private=True)
```

--------------------------------

### Get transactions: get_transactions method

Source: https://python-fints.readthedocs.io/en/latest/_modules/fints/client.html

Fetches transactions for a bank account, preferring MT940-based files and falling back to XML parsing. Handles pending transactions and returns a list of Transaction objects.

```python
    def get_transactions(self, account: SEPAAccount, start_date: datetime.date = None, end_date: datetime.date = None,
                         include_pending = False):
        """
        Fetches the list of transactions of a bank account in a certain timeframe. This prefers using the mt940-based
        files from the bank for historical reasons. However, if they are not available, it falls back to use
        get_transactions_xml and parses the data in a similar way.

        :param account: SEPA
        :param start_date: First day to fetch
        :param end_date: Last day to fetch
        :param include_pending: Include pending transactions (might lack some data like booking day)
        :return: A list of mt940.models.Transaction or fints.models.Transaction objects
        """

        with self._get_dialog() as dialog:
            try:
                hkkaz = self._find_highest_supported_command(HKKAZ5, HKKAZ6, HKKAZ7)
                return self._get_transactions_mt940(dialog, hkkaz, account, start_date, end_date, include_pending)
            except FinTSUnsupportedOperation:
                hkcaz = self._find_highest_supported_command(HKCAZ1)
                response = self._get_transactions_xml(dialog, hkcaz, account, start_date, end_date)

                # If a TAN is required, exit early
                if isinstance(response, NeedTANResponse):
                    return response

                booked_streams, pending_streams = response
                transactions = []
                for s in booked_streams:
                    transactions += [Transaction(t) for t in camt053_to_dict(s)]
                if include_pending:
                    for s in pending_streams:
                        transactions += [Transaction(t) for t in camt053_to_dict(s)]
                return transactions
```

--------------------------------

### Use FinTS3PinTanClient with context manager and state persistence

Source: https://python-fints.readthedocs.io/en/latest/_sources/client.rst.txt

Shows how to use the client as a context manager to keep a standing dialog open for multiple operations, and how to store/restore client state via deconstruct/set_data. The datablob is retrieved from backend storage or set to None, and after the with block, deconstruct() is called to store the updated state.

```python
datablob = ... # get from backend storage, or set to None
client = FinTS3PinTanClient(..., from_data=datablob)

with client:
    accounts = client.get_sepa_accounts()
    balance = client.get_balance(accounts[0])
    transactions = client.get_transactions(accounts[0])

datablob = client.deconstruct()
# Store datablob to backend storage
```

--------------------------------

### Handle TAN/VOP responses and download statements

Source: https://python-fints.readthedocs.io/en/latest/_sources/trouble.rst.txt

This snippet shows a loop that handles NeedTANResponse and NeedVOPResponse by calling ask_for_tan or ask_for_vop. It also demonstrates selecting a statement and downloading it as PDF, with error handling for unsupported operations.

```python
while isinstance(res, NeedTANResponse | NeedVOPResponse):
    if isinstance(res, NeedTANResponse):
        res = ask_for_tan(res)
    elif isinstance(res, NeedVOPResponse):
        res = ask_for_vop(res)

```

```python
elif choice == 11:
    print("Select statement")
    statements = f.get_statements(account)
    for i, statement in enumerate(statements):
        print(i, f"Statement {statement.statement_number}/{statement.year}")
    choice = int(input("Choice: ").strip())
    statement = statements[choice]
    output_pdf = 'statement.pdf'
    res = f.get_statement(account, statement.statement_number, statement.year, StatementFormat.PDF)
    while isinstance(res, NeedTANResponse):
        res = ask_for_tan(res)
    with open(output_pdf, 'wb') as file:
        file.write(res.data)
    print("Written to", output_pdf)
```

--------------------------------

### Get supported TAN mechanisms

Source: https://python-fints.readthedocs.io/en/latest/_sources/tans.rst.txt

Retrieves a dictionary mapping TAN mechanism identifiers (usually three-digit numerals) to TwoStepParametersCommon subclass instances. Use this before any TAN-based operation to see which mechanisms the bank supports.

```python
mechanisms = client.get_tan_mechanisms()
```

--------------------------------

### Handle KeyboardInterrupt when displaying flicker code

Source: https://python-fints.readthedocs.io/en/latest/tans.html

Wrap terminal_flicker_unix in a try/except block to catch KeyboardInterrupts, allowing the user to abort the flicker code display and continue with the TAN. The example passes result.challenge_hhduc as the code argument.

```python
try:
    terminal_flicker_unix(result.challenge_hhduc)
except KeyboardInterrupt:
    pass
```

--------------------------------

### set_product(product_name, product_version)

Source: https://python-fints.readthedocs.io/en/latest/_modules/fints/client.html

Sets the product name and version transmitted during identification with the bank.

```APIDOC
## set_product(product_name, product_version)

### Description
Sets the product name and version that is transmitted as part of the client identification, as required by the FinTS specification.

### Parameters
- **product_name** (string) - Required - The name of the end-user product.
- **product_version** (string) - Required - The version of the end-user product.

### Returns
None

### Example
```python
client.set_product("MyBankingApp", "1.0.0")
```

```

--------------------------------

### Constructor with Positional Arguments

Source: https://python-fints.readthedocs.io/en/latest/developer/working.html

Demonstrates how to pass non-keyword arguments to the constructor, with fields assigned in order, except for header which must be a keyword argument.

```APIDOC
## Constructor with Positional Arguments

### Description
When calling the constructor with non-keyword arguments, fields are assigned in order. The `header` field can only be given as a keyword argument. If no `header` is provided, a default `SegmentHeader` is automatically constructed.

### Method
Constructor

### Endpoint
`fints.segments.HNHBS1(*args, **kwargs)`

### Parameters
#### Constructor Arguments
- **args** (any) - Optional - Positional arguments assigned to fields in order, excluding `header`.
- **header** (SegmentHeader) - Optional - Keyword-only argument for the segment header.

### Request Example
```python
>>> HNHBS1(42)
fints.segments.HNHBS1(header=fints.formals.SegmentHeader('HNHBS', None, 1), message_number=42)
>>> HNHBS1(42, header=SegmentHeader('FOO'))
fints.segments.HNHBS1(header=fints.formals.SegmentHeader('FOO', None, None), message_number=42)
```

### Response
#### Success Response
Returns a new segment object with the specified field values.

#### Response Example
```python
>>> HNHBS1(42)
fints.segments.HNHBS1(header=fints.formals.SegmentHeader('HNHBS', None, 1), message_number=42)
```
```

--------------------------------

### Parse and serialize a FinTS 3.0 message

Source: https://python-fints.readthedocs.io/en/latest/developer/parsing.html

Shows round-trip usage of FinTS3Parser.parse_message and FinTS3Serializer.serialize_message on a FinTS/HBCI 3.0 message. The example is shown as an interactive Python session (>>> prompt) and demonstrates parsing a byte array into a SegmentSequence and serializing it back to bytes.

```python
>>> message = (b'HNHBK:1:3+000000000428+300+430711670077=043999659571CN9D=+2+430711670077=043'
...            b"999659571CN9D=:2'HNVSK:998:3+PIN:1+998+1+2::oIm3BlHv6mQBAADYgbPpp?+kWrAQA+1+"
...            b"2:2:13:@8@00000000:5:1+280:15050500:hermes:S:0:0+0'HNVSD:999:1+@195@HNSHK:2:"
...            b'4+PIN:1+999+1+2::oIm3BlHv6mQBAADYgbPpp?+kWrAQA+1+'
...            b'2:2:13:@8@00000000:5:1+280:15050500:hermes:S:0:0+0\'
```

--------------------------------

### FinTS3Client as context manager

Source: https://python-fints.readthedocs.io/en/latest/_sources/client.rst.txt

Using the client as a context manager keeps a standing dialog open for multiple operations, reducing roundtrips. This is required for two-step TAN transactions.

```APIDOC
## FinTS3Client as context manager

### Description
Using the client as a context manager keeps a standing dialog open for multiple operations, reducing roundtrips. This is required for two-step TAN transactions.

### Usage
python
with client:
    accounts = client.get_sepa_accounts()
    balance = client.get_balance(accounts[0])
    transactions = client.get_transactions(accounts[0])


### Notes
- The client automatically opens and closes dialogs for simple reading operations, but using a context manager keeps the dialog open.
- For TAN transactions, a standing dialog is mandatory because both steps must be in the same dialog.
```

--------------------------------

### Define a FinTS segment class (HNHBS1)

Source: https://python-fints.readthedocs.io/en/latest/developer/segments/index.html

Example segment class definition. Subclasses of FinTS3Segment specify fields as class attributes using DataElementField. The type and version are determined from the class name if it consists of uppercase characters followed by decimal digits.

```python
class HNHBS1(FinTS3Segment):
    message_number = DataElementField(type='num', max_length=4)

```

--------------------------------

### FinTS3Client.__enter__ / __exit__ (context manager)

Source: https://python-fints.readthedocs.io/en/latest/client.html

Use FinTS3Client as a context manager to keep a standing dialog open for multiple operations. The dialog is automatically opened on entry and closed on exit, unless paused.

```APIDOC
## FinTS3Client.__enter__ / __exit__ (context manager)

### Description
Use FinTS3Client as a context manager to keep a standing dialog open for multiple operations. The dialog is automatically opened on entry and closed on exit, unless paused.

### Method
Context manager (with statement)

### Usage
```python
with client:
    accounts = client.get_sepa_accounts()
    balance = client.get_balance(accounts[0])
    transactions = client.get_transactions(accounts[0])
```

### Notes
- Each opening and closing of a dialog takes one FinTS roundtrip.
- For TAN transactions that require both steps in the same dialog, a standing dialog is mandatory.
```

--------------------------------

### resume_dialog method

Source: https://python-fints.readthedocs.io/en/latest/_modules/fints/client.html

Creates a dialog based on data from a previous dialog. The dialog_data must not come from an untrusted source.

```python
    @contextmanager
    def resume_dialog(self, dialog_data):
        """
        Create a dialog based on the data of a previous dialog.

        **Warning:** `dialog_data` **MUST NOT** be from an untrusted source such as user-controlled
        or client-side state or you will have a major security issue.
        """
        if self._standing_dialog:
            raise Exception("Cannot resume dialog, existing standing dialog")
        self._standing_dialog = FinTSDialog.create_resume(self, dialog_data)
        with self._standing_dialog:
            yield self
        self._standing_dialog = None
```

--------------------------------

### set_product method

Source: https://python-fints.readthedocs.io/en/latest/_modules/fints/client.html

Sets the product name and version transmitted as part of identification. According to the FinTS specification, this should contain information about the end-user product, not the FinTS library.

```python
    def set_product(self, product_name, product_version):
        """Set the product name and version that is transmitted as part of our identification

        According to 'FinTS Financial Transaction Services, Schnittstellenspezifikation, Formals',
        version 3.0, section C.3.1.3, you should fill this with useful information about the
        end-user product, *NOT* the FinTS library."""

        self.product_name = product_name
        self.product_version = product_version
```

--------------------------------

### Creating a Segment Object

Source: https://python-fints.readthedocs.io/en/latest/developer/working.html

Demonstrates how to create a FinTS3Segment subclass instance using its constructor, with optional keyword arguments for fields.

```APIDOC
## Creating a Segment Object

### Description
Create a new instance of a FinTS3Segment subclass by calling its constructor. The constructor accepts optional keyword arguments for all fields of the class.

### Method
Constructor

### Endpoint
`fints.segments.HNHBS1()`

### Parameters
#### Constructor Arguments
- **header** (SegmentHeader) - Optional - The segment header. Can only be given as a keyword argument. If omitted, a default SegmentHeader is constructed.
- **message_number** (int) - Optional - The message number.

### Request Example
```python
>>> from fints.segments import HNHBS1
>>> s = HNHBS1()
>>> s
fints.segments.HNHBS1(header=fints.formals.SegmentHeader('HNHBS', None, 1), message_number=None)
```

### Response
#### Success Response
Returns a new segment object with the specified field values.

#### Response Example
```python
>>> s.header.number = 3
>>> s.header
fints.formals.SegmentHeader('HNHBS', 3, 1)
```
```

--------------------------------

### FinTS Client Imports and Constants

Source: https://python-fints.readthedocs.io/en/latest/_modules/fints/client.html

Initial imports and constants for the FinTS client, including bank identifiers and data blob magic bytes.

```python
import datetime
import logging
from abc import ABCMeta, abstractmethod
from base64 import b64decode
from collections import OrderedDict
from contextlib import contextmanager
from decimal import Decimal
from enum import Enum

import bleach
from sepaxml import SepaTransfer

from . import version
from .camt_parser import camt053_to_dict
from .connection import FinTSHTTPSConnection
from .dialog import FinTSDialog
from .exceptions import *
from .formals import (
    CUSTOMER_ID_ANONYMOUS, KTI1, BankIdentifier, DescriptionRequired,
    SynchronizationMode, TANMediaClass4, TANMediaType2,
    SupportedMessageTypes, StatementFormat, TANUsageOption
)
from .message import FinTSInstituteMessage
from .models import SEPAAccount, Transaction
from .parser import FinTS3Serializer
from .security import (
    PinTanDummyEncryptionMechanism, PinTanOneStepAuthenticationMechanism,
    PinTanTwoStepAuthenticationMechanism,
)
from .segments.accounts import HISPA1, HKSPA1
from .segments.auth import HIPINS1, HKTAB4, HKTAB5, HKTAN2, HKTAN3, HKTAN5, HKTAN6, HKTAN7, HIVPPS1, HIVPP1, PSRD1, HKVPA1
from .segments.bank import HIBPA3, HIUPA4, HKKOM4
from .segments.debit import (
    HKDBS1, HKDBS2, HKDMB1, HKDMC1, HKDME1, HKDME2,
    HKDSC1, HKDSE1, HKDSE2, DebitResponseBase,
)
from .segments.depot import HKWPD5, HKWPD6
from .segments.dialog import HIRMG2, HIRMS2, HISYN4, HKSYN3
from .segments.journal import HKPRO3, HKPRO4
from .segments.saldo import HKSAL5, HKSAL6, HKSAL7
from .segments.statement import DKKKU2, HKKAZ5, HKKAZ6, HKKAZ7, HKCAZ1, HKKAU2, HKKAU1, HKEKA3, HKEKA4, HKEKA5
from .segments.transfer import HKCCM1, HKCCS1, HKIPZ1, HKIPM1
from .types import SegmentSequence
from .utils import (
    MT535_Miniparser, Password, SubclassesMixin,
    compress_datablob, decompress_datablob, mt940_to_array,
)

logger = logging.getLogger(__name__)

SYSTEM_ID_UNASSIGNED = '0'
DATA_BLOB_MAGIC = b'python-fints_DATABLOB'
DATA_BLOB_MAGIC_RETRY = b'python-fints_RETRY_DATABLOB'

# workaround for ING not offering PSD2 conform two step authentication
# ING only accepts one step authentication and only allows reading operations
ING_BANK_IDENTIFIER = BankIdentifier(country_identifier='280', bank_code='50010517')
```

--------------------------------

### Find highest supported command: _find_highest_supported_command method

Source: https://python-fints.readthedocs.io/en/latest/_modules/fints/client.html

Searches the BPD for the highest supported version of a segment class. Raises FinTSUnsupportedOperation if no version is found. Optionally returns the parameter segment.

```python
    def _find_highest_supported_command(self, *segment_classes, **kwargs):
        """Search the BPD for the highest supported version of a segment."""
        return_parameter_segment = kwargs.get("return_parameter_segment", False)

        parameter_segment_name = "{}I{}S".format(segment_classes[0].TYPE[0], segment_classes[0].TYPE[2:])
        version_map = dict((clazz.VERSION, clazz) for clazz in segment_classes)
        max_version = self.bpd.find_segment_highest_version(parameter_segment_name, version_map.keys())
        if not max_version:
            raise FinTSUnsupportedOperation('No supported {} version found. I support {}, bank supports {}.'.format(
                parameter_segment_name,
                tuple(version_map.keys()),
                tuple(v.header.version for v in self.bpd.find_segments(parameter_segment_name))
            ))

        if return_parameter_segment:
            return max_version, version_map.get(max_version.header.version)
        else:
            return version_map.get(max_version.header.version)
```

--------------------------------

### Fetch SEPA accounts and handle TAN responses

Source: https://python-fints.readthedocs.io/en/latest/_sources/trouble.rst.txt

Retrieves SEPA accounts, prompting for TAN when needed. If multiple accounts exist, the user selects one interactively; otherwise the single account is used.

```python
# Fetch accounts
        accounts = f.get_sepa_accounts()
        while isinstance(accounts, NeedTANResponse):
            accounts = ask_for_tan(accounts)
        if len(accounts) == 1:
            account = accounts[0]
        else:
            print("Multiple accounts available, choose one")
            for i, mm in enumerate(accounts):
                print(i, mm.iban)
            choice = input("Choice: ").strip()
            account = accounts[int(choice)]
```

```python
        # Test pausing and resuming the dialog
        dialog_data = f.pause_dialog()

    client_data = f.deconstruct(including_private=True)

    f = FinTS3PinTanClient(*client_args, product_id=product_id, from_data=client_data)
    with f.resume_dialog(dialog_data):
        while True:
            operations = [
                "End dialog",
                "Fetch transactions of the last 30 days",
                "Fetch transactions of the last 120 days",
                "Fetch transactions XML of the last 30 days",
                "Fetch transactions XML of the last 120 days",
                "Fetch information",
                "Fetch balance",
                "Fetch holdings",
                "Fetch scheduled debits",
                "Fetch status protocol",
                
```

--------------------------------

### Create and inspect a FinTS3Segment (HNHBS1)

Source: https://python-fints.readthedocs.io/en/latest/_sources/developer/working.rst.txt

Shows how to instantiate a segment object and access its fields. Setting ``header.number`` updates the segment header, and the object prints with its current field values.

```python
>>> from fints.segments import HNHBS1
>>> s = HNHBS1()
>>> s
fints.segments.HNHBS1(header=fints.formals.SegmentHeader('HNHBS', None, 1), message_number=None)
>>> s.header.number = 3
>>> s.header
fints.formals.SegmentHeader('HNHBS', 3, 1)
```

--------------------------------

### Handle TAN request with NeedRetryResponse

Source: https://python-fints.readthedocs.io/en/latest/_sources/tans.rst.txt

Three-step workflow for handling a TAN request: pause the dialog and save client state, prompt for the TAN, then resume the dialog and send the TAN. Use with client and dialog state restoration facilities.

```python
client = FinTS3PinTanClient(...)
# Optionally: choose a tan mechanism with
# client.set_tan_mechanism(…)

with client:
    response = client.sepa_transfer(...)
    
    dialog_data = client.pause_dialog()
client_data = client.deconstruct()
tan_data = response.get_data()
```

```python
tan_request = NeedRetryResponse.from_data(tan_data)
print("TAN request: {}".format(tan_request.challenge))
tan = input('Enter TAN: ')
```

```python
tan_request = NeedRetryResponse.from_data(tan_data)
client = FinTS3PinTanClient(..., from_data=client_data)
with client.resume_dialog(dialog_data):
    response = client.send_tan(tan_request, tan)

print(response.status)
print(response.responses)
```