Why Do I Get the 'UnicodeDecodeError: 'ascii' codec can't decode byte' Error in Python 2.x and How Can I Fix It?

UnicodeDecodeError: 'ascii' Codec Can't Decode Byte

The Problem

When attempting to convert a Python 2.x string containing non-ASCII characters to a Unicode string, you may encounter the "UnicodeDecodeError: 'ascii' codec can't decode byte" error. This occurs because the default behavior is to assume ASCII encoding, which cannot handle non-ASCII characters.

Quick Fix

• Ensure that you decode strings to Unicode strings explicitly.
• Don't assume strings are UTF-8 encoded.
• Convert strings to Unicode strings as early as possible in the code.
• Consider fixing your locale for better Unicode handling.
• Avoid quick reload hacks.

Understanding Unicode in Python 2.x

Unicode strings do not have an encoding and hold Unicode point codes, while strings contain encoded text (e.g., UTF-8, UTF-16). The Markdown module's use of unicode() as a quality gate ensures incoming strings are Unicode strings.

Gotchas and Examples

• Explicit conversion without encoding: unicode('€')
• New style format string into Unicode string: u"The currency is: {}".format('€')
• Old style format string into Unicode string: u'The currency is: %s' % '€'
• Append string to Unicode: u'The currency is: ' '€'

The Unicode Sandwich

Establish a "Unicode sandwich" in your code: decode input data to Unicode, work with Unicode strings, and encode to strings on output. This avoids encoding concerns in the middle of the code.

Input and Decoding

• Define Unicode strings in source code with 'u' prefix (e.g., u'Zürich').
• Set the correct encoding header for source code containing non-ASCII characters (e.g., # encoding: utf-8).
• Use io.open with the appropriate encoding for text file input.
• Utilize backports.csv for handling non-ASCII CSV files.
• Configure databases to return Unicode data.
• Decode HTTP content manually based on the Content-type header's charset.

Output

• print() attempts to encode Unicodes to the console's encoding.
• stdout encoding can be forced with the PYTHONIOENCODING environment variable.
• Use io.open to encode Unicodes to byte strings for file output.

Python 3 Differences

• Python 3's str is a Unicode string.
• Default encoding is UTF-8.
• open() operates in text mode by default, returning decoded str (Unicode ones).

The above is the detailed content of Why Do I Get the 'UnicodeDecodeError: 'ascii' codec can't decode byte' Error in Python 2.x and How Can I Fix It?. For more information, please follow other related articles on the PHP Chinese website!