Python 2.x字符串编码疑问：默认编码与两种声明方式的编码解析

Hey, great question—Python 2's string handling can be super confusing, especially if you're used to Python 3's more straightforward approach. Let's break this down step by step:

First, Let's Clarify Python 2's Two String Types #

Python 2 has two separate string classes, and this is the root of most encoding confusion:

• unicode: Declared with the u prefix (like u'this is a unicode string'), this is an abstract sequence of Unicode characters. It doesn't have a "byte encoding" until you explicitly convert it to a byte string with .encode().
• str: The non-prefixed string (like string = 'this is a string'), this is a byte string—it's just a raw sequence of bytes pulled directly from your source code file.

1. What encoding do strings use in Python 2.x? #

It depends entirely on which string type you're referring to:

• For unicode strings: They store Unicode code points, not bytes. To turn them into a specific byte encoding (like UTF-8 or GBK), you use .encode('encoding_name').
• For str (byte) strings: Their "encoding" is the same as the encoding of your source code file. If you saved your .py file as UTF-8, this string is UTF-8 bytes; if you used GBK, it's GBK bytes.

2. What's the default encoding for encoded strings in Python 2.x? #

The default encoding used for implicit conversions (like when you concatenate a unicode and str, or call str() on a unicode object) is ASCII. You can verify this with a quick snippet:

import sys
print(sys.getdefaultencoding())  # Outputs 'ascii' by default

This is a super common source of UnicodeEncodeError—if your unicode string has non-ASCII characters (like accents or Chinese characters), trying to convert it to str without specifying an encoding will use ASCII and crash.

3. What encoding is the first string (string = 'this is a string')? #

As noted above, this is a byte string, and its encoding matches whatever encoding you saved your source code file in.

If you're unsure what that is, you can test decoding it to unicode with different encodings to see which one works without errors:

my_string = 'this is a string'  # Or your actual string with non-ASCII chars
try:
    print(my_string.decode('utf-8'))
except UnicodeDecodeError:
    print(my_string.decode('gbk'))  # Or another common encoding like latin-1

内容的提问来源于stack exchange，提问作者Cortex