### Install ua-parser with Regex Support

Source: https://github.com/ua-parser/uap-python/blob/master/doc/installation.md

Install the ua-parser library with the recommended regex feature for improved performance. This command adds 'ua-parser[regex]' to your project's dependencies.

```sh
$ pip install 'ua-parser[regex]'
```

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

### Install ua-parser with Regex and YAML Support

Source: https://github.com/ua-parser/uap-python/blob/master/doc/installation.md

Install the ua-parser library with both the regex and PyYaml optional dependencies. This command adds 'ua-parser[regex,yaml]' to your project's dependencies.

```sh
$ pip install 'ua-parser[regex,yaml]'
```

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

### Install ua-parser with RE2 Support

Source: https://github.com/ua-parser/uap-python/blob/master/doc/installation.md

Install the ua-parser library with the google-re2 optional dependency for efficient regex matching. This command adds 'ua-parser[re2]' to your project's dependencies.

```sh
$ pip install 'ua-parser[re2]'
```

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

### Install ua-parser with YAML Support

Source: https://github.com/ua-parser/uap-python/blob/master/doc/installation.md

Install the ua-parser library with the PyYaml optional dependency to enable loading rulesets from YAML files. This command adds 'ua-parser[yaml]' to your project's dependencies.

```sh
$ pip install 'ua-parser[yaml]'
```

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

### Custom foo_resolver Implementation

Source: https://github.com/ua-parser/uap-python/blob/master/doc/guides.md

A bespoke resolver that specifically matches and parses user agent strings starting with 'fooapp/'. It returns a PartialResult with parsed user agent, device, and original UA, or a failure result if the UA does not match.

```python
def foo_resolver(ua: str, domain: Domain, /) -> PartialResult:
    if not ua.startswith('fooapp/'):
        # not our application, match failure
        return PartialResult(domain, None, None, None, ua)

    # we've defined our UA as $appname/$version/$user-token
    app, version, user = ua.split('/', 3)
    major, minor = version.split('.')
    return PartialResult(
        domain,
        UserAgent(app, major, minor),
        None,
        Device(user),
        ua,
    )
```

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

### Set Custom Global Parser

Source: https://github.com/ua-parser/uap-python/blob/master/doc/guides.md

Replace the default global parser with a custom one, affecting all subsequent calls to global parsing functions. This example demonstrates setting a simple custom parser for the 'foo' user agent.

```python
import ua_parser
import ua_parser.loaders

ua_parser.parse("foo")
ua_parser.parser = ua_parser.Parser.from_matchers(
   ua_parser.loaders.load_data((
       [{"regex": "(foo)"}
       ],
       [],
       [],
   ))
)
ua_parser.parse("foo")
```

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

### Load YAML Data for Matchers

Source: https://github.com/ua-parser/uap-python/blob/master/doc/api.md

Loads YAML data structured according to regexes.yaml. The loader parameter allows customization of matcher generation, defaulting to eager matchers but supporting lazy matchers via load_lazy(). Requires PyYAML to be installed.

```python
from ua_parser.loaders import load_yaml
from ua_parser.data import load_data
from pathlib import Path

# Example usage with default eager matchers
matchers = load_yaml(Path("path/to/regexes.yaml"))

# Example usage with lazy matchers
from ua_parser.data import load_lazy

lazy_matchers = load_yaml(Path("path/to/regexes.yaml"), loader=load_lazy)
```

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

### Parser Initialization with FallbackResolver

Source: https://github.com/ua-parser/uap-python/blob/master/doc/guides.md

Demonstrates how to initialize a Parser with a FallbackResolver, prioritizing custom resolvers like foo_resolver before falling back to built-in regex resolvers.

```python
Parser(FallbackResolver([
    foo_resolver,
    regex.Resolver(load_lazy_builtins()),
]))
```

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

### Instantiate Base Resolver

Source: https://github.com/ua-parser/uap-python/blob/master/doc/guides.md

Create a base resolver instance using lazy-loaded built-in regexes. This is the first step in customising parser resolvers.

```python
import ua_parser.loaders
import ua_parser.regex
base = ua_parser.regex.Resolver(
    ua_parser.loaders.load_lazy_builtins())

```

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

### Instantiate LRU Cache

Source: https://github.com/ua-parser/uap-python/blob/master/doc/guides.md

Create an LRU (Least Recently Used) cache with a specified size. This cache will be used to optimize resolver performance.

```python
cache = ua_parser.caching.Lru(10000)

```

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

### Benchmark UA-Parser Resolver Performance

Source: https://github.com/ua-parser/uap-python/blob/master/doc/advanced/caches.md

The `bench` script measures average parse time per input entry by running resolvers with various caches and sizes. It can report results in human-readable text or CSV format.

```bash
python -mua_parser bench
```

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

### Migrate 0.x Parse to 1.0 Parse with Defaults

Source: https://github.com/ua-parser/uap-python/blob/master/doc/advanced/migration.md

Converts a 0.x API `Parse` call to the 1.0 equivalent using `ua_parser.parse` and `with_defaults()`. The 1.0 API returns typed dataclasses, requiring `dataclasses.asdict()` for dictionary output.

```python
from ua_parser import user_agent_parser
from pprint import pprint

ua_string = 'Mozilla/5.0 (Macintosh; Intel Mac OS X 10_9_4) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/41.0.2272.104 Safari/537.36'
pprint(user_agent_parser.Parse(ua_string))
```

```python
import dataclasses
import ua_parser
from pprint import pprint

ua_string = 'Mozilla/5.0 (Macintosh; Intel Mac OS X 10_9_4) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/41.0.2272.104 Safari/537.36'
pprint(dataclasses.asdict(ua_parser.parse(ua_string).with_defaults()))
```

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

### Load Custom Ruleset with YAML

Source: https://github.com/ua-parser/uap-python/blob/master/doc/guides.md

Load a custom ruleset from a YAML file to create a new parser instance. Requires the PyYAML package.

```python
from ua_parser import Parser
from ua_parser.loaders import load_yaml # requires PyYaml

parser = Parser.from_matchers(load_yaml("regexes.yaml"))
parser.parse(some_ua)
```

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

### Add Legacy YAML Ruleset Support in 1.0

Source: https://github.com/ua-parser/uap-python/blob/master/doc/advanced/migration.md

A shim to load a YAML ruleset from the UA_PARSER_YAML environment variable and set it as the global parser for the 1.0 API.

```python
import ua_parser
from ua_parser.loaders import load_yaml
import os

if yaml_path := os.environ.get("UA_PARSER_YAML"):
    ua_parser.parser = ua_parser.Parser.from_matchers(
        load_yaml(yaml_path))
```

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

### Cache Performance Analysis Chart

Source: https://github.com/ua-parser/uap-python/wiki/Cache-Analysis-History

A Mermaid chart visualizing the average performance (in milliseconds) of different cache algorithms across various cache sizes. This chart helps in understanding the relative performance of each algorithm.

```mermaid
--- 
config:
    xyChart:
        width: 1200
        height: 500
--- 
xychart-beta
    x-axis "cache size" [10, 20, 50, 100, 200, 500, 1000, 2000, 5000]
    y-axis "average (ms)" 0 --> 500
    line "test" [420, 420, 420, 420, 420, 420, 420, 420, 420]
    line [419, 423, 407, 398, 391, 354, 309, 262, 203]
    line [418, 419, 407, 392, 371, 330, 284, 236, 178]
    line [420, 417, 417, 388, 371, 326, 283, 238, 180]
    line [417, 415, 407, 385, 363, 300, 251, 205, 153]
    line [415, 412, 404, 384, 358, 293, 246, 200, 150]
    line [414, 411, 402, 388, 370, 326, 283, 237, 180]
    line [414, 409, 402, 384, 362, 302, 253, 205, 153]
    line [415, 411, 401, 383, 362, 296, 247, 200, 150]
    line [424, 412, 404, 386, 364, 310, 261, 213, 158]
    line [414, 399, 385, 341, 311, 257, 219, 185, 156]
    line [413, 398, 377, 339, 309, 253, 216, 184, 146]
    line [410, 392, 365, 341, 304, 253, 216, 185, 162]
    line [410, 390, 365, 336, 305, 252, 214, 185, 157]
    line [412, 390, 361, 338, 304, 250, 211, 181, 147]
```

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

### Measure UA-Parser Cache Hit Rates

Source: https://github.com/ua-parser/uap-python/blob/master/doc/advanced/caches.md

Use the `hitrates` script to measure the hit rates and memory overhead of UA-parser's caches at various sizes. It simulates cache usage on a sample file and includes BELÁDY’s MIN for theoretical upper bounds.

```bash
python -mua_parser hitrates
```

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

### Set Custom Parser with Caching Resolver

Source: https://github.com/ua-parser/uap-python/blob/master/doc/guides.md

Wrap a custom resolver (including caching) in a Parser instance and set it as the global parser. This applies the new configuration to all library users.

```python
ua_parser.parser = ua_parser.Parser(resolver)

```

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

### Parse User Agent String for All Data

Source: https://github.com/ua-parser/uap-python/blob/master/README.rst

Use the `parse` function to extract all available information (user agent, OS, device) from a user agent string. If data is not found, it will be set to None.

```python
>>> from ua_parser import parse
>>> ua_string = 'Mozilla/5.0 (Macintosh; Intel Mac OS X 10_9_4) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/41.0.2272.104 Safari/537.36'
>>> parse(ua_string) # doctest: +NORMALIZE_WHITESPACE, +ELLIPSIS
Result(user_agent=UserAgent(family='Chrome',
                                major='41',
                                minor='0',
                                patch='2272',
                                patch_minor='104'),
           os=OS(family='Mac OS X',
                 major='10',
                 minor='9',
                 patch='4',
                 patch_minor=None),
           device=Device(family='Mac',
                         brand='Apple',
                         model='Mac'),
           string='Mozilla/5.0 (Macintosh; Intel Mac OS...)

>>> parse("")
Result(user_agent=None, os=None, device=None, string='')
```

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

### Parse Full User-Agent String

Source: https://github.com/ua-parser/uap-python/blob/master/doc/quickstart.md

Use the `parse` function to extract all available data (user agent, OS, device) from a user-agent string. Returns `None` for any data not found.

```python
>>> from ua_parser import parse
>>> ua_string = 'Mozilla/5.0 (Macintosh; Intel Mac OS X 10_9_4) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/41.0.2272.104 Safari/537.36'
>>> parse(ua_string)
Result(user_agent=UserAgent(family='Chrome',
                            major='41',
                            minor='0',
                            patch='2272',
                            patch_minor='104'),
       os=OS(family='Mac OS X',
             major='10',
             minor='9',
             patch='4',
             patch_minor=None),
       device=Device(family='Mac',
                     brand='Apple',
                     model='Mac'),
       string='Mozilla/5.0 (Macintosh; Intel Mac OS...)
```

```python
>>> parse("")
Result(user_agent=None, os=None, device=None, string='')
```

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

### Compose Caching Resolver

Source: https://github.com/ua-parser/uap-python/blob/master/doc/guides.md

Combine a base resolver with an LRU cache to create a caching resolver. This enhances performance by storing recent results.

```python
resolver = ua_parser.caching.CachingResolver(
    base,
    cache
)

```

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

### FallbackResolver Class Implementation

Source: https://github.com/ua-parser/uap-python/blob/master/doc/guides.md

A higher-order resolver that attempts to resolve a user agent string by sequentially calling a list of sub-resolvers until a match is found. It returns the result from the first successful resolver or a failure result if no resolver matches.

```python
class FallbackResolver:
    def __init__(self, resolvers: List[Resolver]) -> None:
        self.resolvers = resolvers

    def __call__(self, ua: str, domain: Domain, /) -> PartialResult:
        if domain:
            for resolver in self.resolvers:
                r = resolver(ua, domain)
                # if any value is non-none the resolver found a match
                if r.user_agent_string is not None \
                  or r.os is not None \
                  or r.device is not None:
                    return r

        # if no resolver found a match (or nothing was requested),
        # resolve to failure
        return PartialResult(domain, None, None, None, ua)
```

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

### ua_parser.loaders.load_yaml

Source: https://github.com/ua-parser/uap-python/blob/master/doc/api.md

Loads YAML data following the regexes.yaml structure to create matchers for user agent parsing. It supports custom data loaders for generating different matcher variants.

```APIDOC
## ua_parser.loaders.load_yaml(f: PathOrFile, loader: DataLoader = load_data)

### Description
Loads YAML data following the `regexes.yaml` structure. The `loader` parameter customizes which matcher variant is generated; by default, `load_data()` is used to generate eager matchers, and `load_lazy()` can be used to generate lazy matchers instead.

### Parameters
#### Path Parameters
- **f** (PathOrFile) - Required - The path or file object to load YAML data from.
- **loader** (DataLoader) - Optional - The data loader function to use for generating matchers. Defaults to `load_data`.

#### WARNING
Only available if [`PyYaml`](https://pyyaml.org) is installed.
```

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

### Force Initialization of Global Parser

Source: https://github.com/ua-parser/uap-python/blob/master/doc/advanced/migration.md

Explicitly access the global parser on load to avoid unexpected runtime loads caused by lazy instantiation in the 1.0 API.

```python
import ua_parser
# force initialisation of global parser
ua_parser.parser
```

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

### Resolver Protocol Definition

Source: https://github.com/ua-parser/uap-python/blob/master/doc/guides.md

Defines the structural protocol for a resolver, which is a callable that accepts a user agent string and a domain, returning a PartialResult.

```python
class Resolver(Protocol):
    @abc.abstractmethod
    def __call__(self, ua: str, domain: Domain, /) -> PartialResult:
        ...
```

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

### Extract OS Information

Source: https://github.com/ua-parser/uap-python/blob/master/doc/quickstart.md

Use the `parse_os` function to extract only the operating system details from a user-agent string. Returns `None` for missing data.

```python
>>> from ua_parser import parse_os
>>> ua_string = 'Mozilla/5.0 (Macintosh; Intel Mac OS X 10_9_4) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/41.0.2272.104 Safari/537.36'
>>> parse_os(ua_string)
OS(family='Mac OS X', major='10', minor='9', patch='4', patch_minor=None)
```

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

### Extract Device Information

Source: https://github.com/ua-parser/uap-python/blob/master/doc/quickstart.md

Use the `parse_device` function to extract only the device details from a user-agent string. Returns `None` for missing data.

```python
>>> from ua_parser import parse_device
>>> ua_string = 'Mozilla/5.0 (Macintosh; Intel Mac OS X 10_9_4) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/41.0.2272.104 Safari/537.36'
>>> parse_device(ua_string)
Device(family='Mac', brand='Apple', model='Mac')
```

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

### Python Object Memory Analysis: Class without __slots__

Source: https://github.com/ua-parser/uap-python/blob/master/doc/advanced/caches.md

Illustrates the memory overhead of a Python object without `__slots__`. This includes an instance dictionary, measured as of Python 3.11 on a 64-bit platform.

```python
class:
    # Without __slots__, a Python object is 48 bytes plus an instance dict.
    pass
```

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

### Deque Space Requirement Formula

Source: https://github.com/ua-parser/uap-python/blob/master/doc/advanced/caches.md

This formula estimates the memory usage for a deque based on the number of elements (n). It considers the fixed metadata size and the space for blocks, where each block holds up to 64 items.

```text
232 + max(1, ceil(n / 64)) * 66 * 8
```

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

### Python Object Memory Analysis: Class with __slots__

Source: https://github.com/ua-parser/uap-python/blob/master/doc/advanced/caches.md

Demonstrates the memory overhead of a Python object using `__slots__`. This calculation is specific to Python 3.11 on a 64-bit platform and excludes the size of stored data.

```python
class:
    # With __slots__, a Python object is 32 bytes + 8 bytes for each member.
    # An additional 8 bytes is necessary for weakref support (slotted objects in UA-Parser don’t have weakref support).
    pass
```

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

### OrderedDict Space Requirement Formula

Source: https://github.com/ua-parser/uap-python/blob/master/doc/advanced/caches.md

This formula estimates the memory usage for an OrderedDict based on the number of elements (n). It accounts for the underlying dictionary, linked list nodes, and overhead.

```text
dict(n) + 64 + 8 * 2**(ceil(log2(n)) + 1) + 32 * n
```

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

### Extract Browser Data from User Agent String

Source: https://github.com/ua-parser/uap-python/blob/master/README.rst

Use the `parse_user_agent` function to specifically extract only the browser information from a user agent string. Returns None if no browser data is found.

```python
>>> from ua_parser import parse_user_agent
>>> ua_string = 'Mozilla/5.0 (Macintosh; Intel Mac OS X 10_9_4) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/41.0.2272.104 Safari/537.36'
>>> parse_user_agent(ua_string)
UserAgent(family='Chrome', major='41', minor='0', patch='2272', patch_minor='104')

>>> parse_user_agent("")
```

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

### Extract Browser Data

Source: https://github.com/ua-parser/uap-python/blob/master/doc/quickstart.md

Use the `parse_user_agent` function to specifically extract only the browser information from a user-agent string. Returns `None` for missing data.

```python
>>> from ua_parser import parse_user_agent
>>> ua_string = 'Mozilla/5.0 (Macintosh; Intel Mac OS X 10_9_4) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/41.0.2272.104 Safari/537.36'
>>> parse_user_agent(ua_string)
UserAgent(family='Chrome', major='41', minor='0', patch='2272', patch_minor='104')
```

```python
>>> parse_user_agent("")
```

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