How to Strip Non-Printable Characters from Strings in Python?

Stripping Non-Printable Characters from a String in Python

In Perl, the s/[^[:print:]]//g regex effectively removes all non-printable characters from a string. However, in Python, there is no equivalent POSIX regex class, leaving some wondering how to accomplish the same task.

Understanding Unicode

The challenge lies in handling Unicode characters, as the string.printable method may unintentionally strip them out.

Building a Custom Character Class

To address this, we can construct a custom character class using the unicodedata module. The unicodedata.category() function provides insights into character categories. For example, we can define a character class called control_characters to represent non-printable characters like control characters and surrogate characters by filtering out those categories from the Unicode character set.

<code class="python">import unicodedata
import re

categories = {'Cc', 'Cf', 'Cs'}  # Include desired categories here
control_chars = ''.join(chr(i) for i in range(sys.maxunicode) if unicodedata.category(chr(i)) in categories)
control_char_re = re.compile('[%s]' % re.escape(control_chars))</code>

This approach offers improved efficiency compared to iterating over strings.

<code class="python">def remove_control_chars(s):
    return control_char_re.sub('', s)</code>

Additional Customization

For scenarios where filtering additional categories (e.g., private-use characters) is necessary, you can expand the character class accordingly.

<code class="python">categories.add('Co')  # Add private-use characters
# Rebuild the character class and regex</code>

By utilizing this approach, you can effectively strip non-printable characters from Unicode strings in Python, catering to both basic and customized use cases.

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