How can I check if a string contains only ASCII alphanumeric characters and underscores in Python?
Antek N

To check if a string contains only ASCII alphanumeric characters (uppercase or lowercase), as well as underscores, in Python, you can use various approaches. Here's a long-form explanation of different methods to accomplish this: 1. Using String Methods and ASCII Ranges: - One approach is to iterate over each character in the string using afor loop and check if each character is an ASCII alphanumeric character (using theisalnum() method) or an underscore character. - Additionally, you can use theord() function to obtain the Unicode code point of each character and check if it falls within the ASCII range. - If any character fails these checks, returnFalse. If all characters are ASCII alphanumeric characters or underscores, returnTrue. - Example:

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def contains_only_ascii_alphanumeric_and_underscore(string):
    for char in string:
   if not char.isalnum() and char != '_':
  return False
   if ord(char) > 127:
  return False
    return True

2. Using Regular Expressions: - Regular expressions can be used to match and validate the format of the string. - Import there module and define a regular expression pattern that matches only ASCII alphanumeric characters (uppercase or lowercase) and underscores. - The patternr'^[A-Za-z0-9_]+$' matches a string consisting of one or more ASCII alphanumeric characters (uppercase or lowercase) and underscores. - Use there.match() function to check if the entire string matches the pattern. - If it matches, returnTrue; otherwise, returnFalse. - Example:

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import re

def contains_only_ascii_alphanumeric_and_underscore(string):
    pattern = r'^[A-Za-z0-9_]+$'
    return bool(re.match(pattern, string))

Choose the method that best suits your requirements. Each approach checks if a string contains only ASCII alphanumeric characters and underscores, but they differ in terms of validation criteria, supported formats, and potential overhead.

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