How do I check whether a file exists without exceptions?

Understanding the best check

Choosing the correct method to confirm the existence of a file or directory is crucial. os.path.exists() is your friend when you want to know if any path exists, including directories. For an extra layer of certainty ensuring readability, pair up os.path.isfile() with os.access(file_path, os.R_OK).

import os
# Double check if file exists and is as readable as a well-commented code!
file_readable = os.path.isfile('your/file.txt') and os.access('your/file.txt', os.R_OK)
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To deal with files and directories with OOP finesse, pathlib in Python 3.4 and above could be your savior. With pathlib, you can juggle file checks and path manipulations like a pro.

Coping with race conditions

Watch out for those sneaky race conditions. If you're trying to open a file right after confirming it's there, bad news: it might get deleted or modified between your check and the open call. Avoid this blunder by encapsulating the open call in a try block.

try:
    with open('your/file.txt', 'r') as file:
        # Alrighty, let's read some classified info!
except FileNotFoundError:
    # Oops, our treasure hunt ends here!
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Advanced pathlib tricks

For advanced users, pathlib offers a .resolve(strict=True) method, which can be used inside a try block. This function throws a FileNotFoundError if the file is absent, mimicking the open method's behavior.

from pathlib import Path
try:
    file_path = Path('your/file.txt').resolve(strict=True)
except FileNotFoundError:
    # Time to switch to plan B: The file is MIA!
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Navigating symbolic links and permissions

os.path.exists() smoothly navigates symbolic links, returning True if the link points to an existing file or directory. Also, it's critical to consider read/write permissions. os.access() lets you confirm these access rights:

import os
# Confirm file existence and permissions (because trespassing is not cool, right?)
file_has_permissions = os.path.exists('your/file.txt') and os.access('your/file.txt', os.R_OK | os.W_OK)
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Just as you'd ensure you can check out a book from the library, confirm you have the necessary permissions for the file.

pathlib for directory goodness

Beyond files, pathlib provides the is_dir() method for directories. This treats directory-checking as a first-class operation, similar to file-checking.

from pathlib import Path
# Directory check: Because it's not just files that matter!
directory_exists = Path('your/directory').is_dir()
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It ensures the section (directory) in your library exists before you go hunting for books (files).