### Install pathtype

Source: https://context7.com/xfrenette/pathtype/llms.txt

Use pip to install the package.

```bash
pip install pathtype
```

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

### Create an OR Validator with pathtype.validation.Any

Source: https://github.com/xfrenette/pathtype/blob/main/README.md

Combine validators using 'Any' to create a validator that passes if any of its constituent validators succeed. This example checks if the file name contains 'a' OR does not contain 'b'.

```python
from pathtype.validation import Any

or_validator = Any(must_have_a, must_not_have_b)

parser.add_argument(
    ...
    type=pathtype.Path(validator=or_validator)
)
```

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

### Manually Control Validation Order with Custom Exists Validator

Source: https://github.com/xfrenette/pathtype/blob/main/README.md

To change validation order, instantiate predefined validators like Exists and include them in the 'validator' list. This example runs the custom validator before checking existence.

```python
from pathtype.validation import Exists

exist_validator = Exists()

parser.add_argument(
    ...
    type=pathtype.Path(validator=[must_not_have_b, exist_validator])
)
```

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

### Validate Non-Existent Text File Creation

Source: https://github.com/xfrenette/pathtype/blob/main/README.md

Combine multiple pathtype validations to ensure a file argument is a text file (*.txt), does not already exist, and that the user has permissions to create it. This implies the parent directory exists.

```python
parser.add_argument(
    "--file",
    type=pathtype.Path(not_exists=True, creatable=True, name_matches_glob="*.txt")
)
args = parser.parse_args(["--file", "path/to/my_file.txt"])
```

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

### Validate file creation

Source: https://context7.com/xfrenette/pathtype/llms.txt

Ensures a file can be created by checking parent directory permissions.

```python
import argparse
import pathtype

parser = argparse.ArgumentParser()

# Validate file can be created (parent dir exists and is writable)
parser.add_argument("--new-file", type=pathtype.Path(creatable=True))

# Validate file is writable OR can be created if it doesn't exist
parser.add_argument("--output", type=pathtype.Path(writable_or_creatable=True))

args = parser.parse_args(["--new-file", "/tmp/new_data.json", "--output", "/tmp/results.csv"])
print(args.new_file.parent.exists())  # True
```

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

### Define path arguments with pathtype

Source: https://context7.com/xfrenette/pathtype/llms.txt

Use pathtype.Path to enforce constraints like file existence and naming patterns during argument parsing.

```python
parser.add_argument(
    "--output",
    required=True,
    type=pathtype.Path(
        not_exists=True,
        creatable=True,  # implies parent_exists=True
        name_matches_glob="*.csv"
    )
)

# Example usage
args = parser.parse_args(["--input", "data.json", "--output", "results.csv"])
print(f"Reading from: {args.input}")
print(f"Writing to: {args.output}")
```

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

### Validate file existence

Source: https://context7.com/xfrenette/pathtype/llms.txt

Checks if a path exists, does not exist, or if its parent directory exists.

```python
import argparse
import pathtype

parser = argparse.ArgumentParser()

# Validate file exists
parser.add_argument("--input", type=pathtype.Path(exists=True))

# Validate file does NOT exist (for output files)
parser.add_argument("--output", type=pathtype.Path(not_exists=True))

# Validate parent directory exists (file may or may not exist)
parser.add_argument("--log", type=pathtype.Path(parent_exists=True))

# Example usage
args = parser.parse_args(["--input", "/etc/hosts", "--output", "new_file.txt", "--log", "/tmp/myapp.log"])
print(args.input.exists())  # True
```

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

### Combine Predefined Exists Validation with Custom Validator

Source: https://github.com/xfrenette/pathtype/blob/main/README.md

Use the 'exists=True' argument in pathtype.Path to validate file existence before custom validation. Custom validators run after predefined ones.

```python
parser.add_argument(
    ...
    type=pathtype.Path(validator=must_not_have_b, exists=True)
)
```

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

### Use built-in validation classes

Source: https://context7.com/xfrenette/pathtype/llms.txt

Utilize classes from pathtype.validation to control the order and granularity of path validation.

```python
import argparse
import pathlib
import pathtype
from pathtype.validation import (
    Exists, NotExists, UserReadable, UserWritable,
    UserExecutable, ParentExists, ParentUserWritable,
    NameMatches, PathMatches
)

# Create validator instances
exists = Exists()
readable = UserReadable()
name_pattern = NameMatches(pattern=r"\.txt$")

# Custom validator
def validate_not_empty(path: pathlib.Path, arg: str):
    if path.exists() and path.stat().st_size == 0:
        raise argparse.ArgumentTypeError(f"file is empty: {arg}")

# Control validation order: name pattern first, then existence, then custom
validators = [name_pattern, exists, readable, validate_not_empty]

parser = argparse.ArgumentParser()
parser.add_argument("--file", type=pathtype.Path(validator=validators))

args = parser.parse_args(["--file", "document.txt"])
```

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

### Convert CLI arguments to pathlib.Path

Source: https://context7.com/xfrenette/pathtype/llms.txt

Converts string arguments to pathlib.Path instances without performing any validation.

```python
import argparse
import pathtype

parser = argparse.ArgumentParser()
parser.add_argument("input_file", type=pathtype.Path())

args = parser.parse_args(["my_data.csv"])
print(type(args.input_file))  # <class 'pathlib.PosixPath'>
print(args.input_file)  # my_data.csv
```

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

### Use Single and Multiple Custom Validators with Path

Source: https://github.com/xfrenette/pathtype/blob/main/README.md

Integrate custom validators using the 'validator' parameter of pathtype.Path. Pass a single validator or a list for sequential execution.

```python
parser = argparse.ArgumentParser()
parser.add_argument(
    "--path-1",
    type=pathtype.Path(validator=must_have_a)
)
parser.add_argument(
    "--path-2",
    type=pathtype.Path(validator=[must_have_a, must_not_have_b])
)
```

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

### Create Custom Validators for File Name Checks

Source: https://github.com/xfrenette/pathtype/blob/main/README.md

Define functions that validate path names. 'must_have_a' checks for the presence of 'a', while 'must_not_have_b' ensures 'b' is absent. Both raise ArgumentTypeError if validation fails.

```python
def must_have_a(path: pathlib.Path, arg: str):
    """Custom validator that fails if the file name doesn't contain the letter 'a'."""
    if "a" not in path.name:
        raise argparse.ArgumentTypeError('The file name must have the letter "a"')

def must_not_have_b(path: pathlib.Path, arg: str):
    """Custom validator that fails if the file name contains the letter 'b'."""
    if "b" in path.name:
        raise argparse.ArgumentTypeError('The file name must NOT have the letter "b"')

```

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

### Validate file names with patterns

Source: https://context7.com/xfrenette/pathtype/llms.txt

Uses regular expressions or glob patterns to validate file names or full paths.

```python
import argparse
import pathtype

parser = argparse.ArgumentParser()

# Match file extension using regular expression
parser.add_argument(
    "--image",
    type=pathtype.Path(name_matches_re=r"\.(png|jpe?g|gif)$")
)

# Match file extension using glob pattern
parser.add_argument(
    "--config",
    type=pathtype.Path(name_matches_glob="*.json")
)

# Match full path using regular expression
parser.add_argument(
    "--log",
    type=pathtype.Path(path_matches_re=r"/var/log/.+\.log$")
)

# Match full path using glob pattern
parser.add_argument(
    "--data",
    type=pathtype.Path(path_matches_glob="/home/*/*.csv")
)

# Example: Image file validation
args = parser.parse_args(["--image", "photo.jpeg", "--config", "settings.json"])
print(args.image.suffix)  # .jpeg
```

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

### Combine validators with logical operators

Source: https://context7.com/xfrenette/pathtype/llms.txt

Use Any and All classes to create complex validation rules by combining multiple validator instances.

```python
import argparse
import pathtype
from pathtype.validation import Any, All, Exists, UserReadable, NameMatches

# Accept either JSON or YAML config files
json_validator = NameMatches(glob="*.json")
yaml_validator = NameMatches(glob="*.yaml")
config_format = Any(json_validator, yaml_validator)

parser = argparse.ArgumentParser()
parser.add_argument(
    "--config",
    type=pathtype.Path(
        validator=[Exists(), UserReadable(), config_format]
    )
)

# More complex: file must exist AND (be readable OR be in /tmp)
import pathlib

def is_in_tmp(path: pathlib.Path, arg: str):
    if not str(path.resolve()).startswith("/tmp"):
        raise argparse.ArgumentTypeError("path not in /tmp")

readable_or_tmp = Any(UserReadable(), is_in_tmp)
complex_validator = All(Exists(), readable_or_tmp)

parser.add_argument(
    "--data",
    type=pathtype.Path(validator=complex_validator)
)

args = parser.parse_args(["--config", "app.yaml", "--data", "/tmp/data.bin"])
```

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

### Validate file permissions

Source: https://context7.com/xfrenette/pathtype/llms.txt

Checks for read, write, or execute permissions using the current user's effective permissions.

```python
import argparse
import pathtype

parser = argparse.ArgumentParser()

# Validate file is readable (implies exists=True)
parser.add_argument("--config", type=pathtype.Path(readable=True))

# Validate file is writable (implies exists=True)
parser.add_argument("--data", type=pathtype.Path(writable=True))

# Validate file is executable (implies exists=True)
parser.add_argument("--script", type=pathtype.Path(executable=True))

# Combine multiple permissions
parser.add_argument("--file", type=pathtype.Path(readable=True, writable=True))

# Example usage
args = parser.parse_args([
    "--config", "/etc/hosts",
    "--data", "/tmp/output.txt",
    "--script", "/usr/bin/python3",
    "--file", "/tmp/test.txt"
])
```

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

### Implement CLI Path Validation with pathtype

Source: https://context7.com/xfrenette/pathtype/llms.txt

Integrate pathtype into an argparse parser to enforce file existence, readability, and naming conventions. The resulting arguments are returned as validated pathlib.Path objects.

```python
#!/usr/bin/env python3
"""File converter CLI with comprehensive path validation."""

import argparse
import pathlib
import pathtype
from pathtype.validation import Any, NameMatches

def main():
    parser = argparse.ArgumentParser(
        description="Convert data files between formats"
    )

    # Input: must exist, be readable, be JSON or CSV
    input_format = Any(
        NameMatches(glob="*.json"),
        NameMatches(glob="*.csv")
    )
    parser.add_argument(
        "-i", "--input",
        required=True,
        help="Input file (JSON or CSV)",
        type=pathtype.Path(readable=True, validator=input_format)
    )

    # Output: writable or creatable, must be JSON or CSV
    output_format = Any(
        NameMatches(glob="*.json"),
        NameMatches(glob="*.csv")
    )
    parser.add_argument(
        "-o", "--output",
        required=True,
        help="Output file (JSON or CSV)",
        type=pathtype.Path(writable_or_creatable=True, validator=output_format)
    )

    # Optional log file
    parser.add_argument(
        "--log",
        help="Log file path",
        type=pathtype.Path(writable_or_creatable=True, name_matches_glob="*.log")
    )

    args = parser.parse_args()

    # At this point, all paths are validated pathlib.Path instances
    print(f"Input: {args.input} (exists: {args.input.exists()})")
    print(f"Output: {args.output}")
    if args.log:
        print(f"Log: {args.log}")

    # Proceed with file conversion...
    input_data = args.input.read_text()
    # ... process data ...

if __name__ == "__main__":
    main()

# Usage:
# python converter.py -i data.json -o output.csv --log conversion.log
#
# Error examples:
# python converter.py -i missing.json -o out.csv
#   error: argument -i/--input: file doesn't exist (missing.json)
#
# python converter.py -i data.txt -o out.csv
#   error: argument -i/--input: glob "*.json" doesn't match data.txt
```

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

### Validate Image File Argument

Source: https://github.com/xfrenette/pathtype/blob/main/README.md

Use pathtype.Path as the type for an argparse argument to validate that the provided image file exists, is readable, and has a supported extension (PNG, GIF, JPEG).

```python
import argparse
import pathtype

if __name__ == "__main__":
    parser = argparse.ArgumentParser()
    # We use `pathtype.Path` as the `type` argument to validate that the --image 
    # argument is a readable image file (checks the file extension).
    parser.add_argument(
        "--image", required=True,
        help="Image file to open (PNG, GIF or JPEG supported)",
        type=pathtype.Path(readable=True, name_matches_re=r"\.(png|jpe?g|gif)$")
    )
 
    # Path validations are done automatically by calling the next line, no need to 
    # add code to validate that the path can be read and that it has the correct 
    # extension. 
    args = parser.parse_args()
    
    # args.image is an instance of pathlib.Path. And since using `readable` implies 
    # `exists`, we know the file already exists and is readable by the current user.
    print(args.image.exists())
    # True
```

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

### Combine multiple validation rules

Source: https://context7.com/xfrenette/pathtype/llms.txt

Applies multiple constraints to a single argument.

```python
import argparse
import pathtype

parser = argparse.ArgumentParser()

# Input file: must exist, be readable, and be a JSON file
parser.add_argument(
    "--input",
    required=True,
    type=pathtype.Path(
        readable=True,  # implies exists=True
        name_matches_glob="*.json"
    )
)
```

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

### Convert Argument to Pathlib.Path

Source: https://github.com/xfrenette/pathtype/blob/main/README.md

Use pathtype.Path() as the type for an argparse argument to automatically convert the provided string argument into a pathlib.Path instance.

```python
parser.add_argument(
  "my_arg", type=pathtype.Path()
)

args = parser.parse_args()
print(type(args.my_arg))  # >>> <class 'pathlib.PosixPath'>
```

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

### Implement custom path validators

Source: https://context7.com/xfrenette/pathtype/llms.txt

Define custom functions to perform complex validation logic on path objects, which can be passed individually or as a list to the validator parameter.

```python
import argparse
import pathlib
import pathtype

def validate_max_size(path: pathlib.Path, arg: str):
    """Validate file is smaller than 10MB."""
    if path.exists():
        size_mb = path.stat().st_size / (1024 * 1024)
        if size_mb > 10:
            raise argparse.ArgumentTypeError(
                f"file too large: {size_mb:.1f}MB (max 10MB)"
            )

def validate_in_home_dir(path: pathlib.Path, arg: str):
    """Validate path is inside user's home directory."""
    import os
    resolved = pathlib.Path(os.path.abspath(os.path.expanduser(path)))
    home = pathlib.Path.home()
    if not str(resolved).startswith(str(home)):
        raise argparse.ArgumentTypeError(
            f"path must be in home directory: {resolved}"
        )

parser = argparse.ArgumentParser()

# Single custom validator
parser.add_argument(
    "--input",
    type=pathtype.Path(validator=validate_max_size, exists=True)
)

# Multiple custom validators (executed sequentially)
parser.add_argument(
    "--output",
    type=pathtype.Path(validator=[validate_in_home_dir, validate_max_size])
)

args = parser.parse_args(["--input", "data.txt", "--output", "~/results.txt"])
```

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

### Define a Custom Path Validator Function

Source: https://github.com/xfrenette/pathtype/blob/main/README.md

Custom validators must accept a pathlib.Path object and the original string argument. Raise argparse.ArgumentTypeError, TypeError, or ValueError on failure. Return nothing on success.

```python
def validator(path: pathlib.Path, arg: str) -> None:
    pass
```

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

### Custom Validator for Home Directory Path

Source: https://github.com/xfrenette/pathtype/blob/main/README.md

This validator checks if a provided path is located within the user's home directory. It raises an ArgumentTypeError if the path is outside the home directory. Ensure the path is expanded and resolved before comparison.

```python
import os.path
import pathlib
import argparse
import pathtype


def is_inside_home_dir(path: pathlib.Path, arg: str):
    """Validate that the path is inside the current user's home directory."""
    expanded_path = os.path.expanduser(path)
    resolved_path = pathlib.Path(os.path.abspath(expanded_path))
    user_dir = pathlib.Path.home()
    # We check that `resolved_path` starts with the same directories as `user_dir`
    is_child = resolved_path.parts[:len(user_dir.parts)] == user_dir.parts
    
    if not is_child:
        raise argparse.ArgumentTypeError(
            f"path ({resolved_path}) is not in the user's home directory ({user_dir})"
        )

```

```python
if __name__ == "__main__":
    parser = argparse.ArgumentParser()
    parser.add_argument(
        "--path",
        type=pathtype.Path(validator=is_inside_home_dir)
    )

    # The following line won't raise any error
    args = parser.parse_args(["--path", "~/valid/path"])
    print(repr(args.path))
    # PosixPath('~/valid/path')

    # The following line will fail since the path is not inside the user's directory
    args = parser.parse_args(["--path", "/at-root"])
    # Fails with this message:
    #   usage: example.py [-h] [--path PATH]
    #   example.py: error: argument --path: path (/at-root) is not in the user's home directory (/home/user)

```

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