为什么 Popen.communicate() 返回 b'hi ' 而不是 'hi'? [英] Why does Popen.communicate() return b'hi ' instead of 'hi'?

问题描述

有人能解释一下为什么我想要的结果hi"前面有一个字母b"，后面有一个换行符吗?

Can someone explain why the result I want, "hi", is preceded with a letter 'b' and followed with a newline?

我正在使用 Python 3.3

>>> import subprocess
>>> print(subprocess.Popen("echo hi", shell=True,
                           stdout=subprocess.PIPE).communicate()[0])
b'hi
'

如果我使用 python 2.7 运行它，则不会出现这个额外的b"

This extra 'b' does not appear if I run it with python 2.7

推荐答案

echo 命令默认返回换行符

The echo command by default returns a newline character

比较一下:

print(subprocess.Popen("echo -n hi", 
    shell=True, stdout=subprocess.PIPE).communicate()[0])

字符串前面的b表示它是一个字节序列，相当于Python 2.6+中的普通字符串

As for the b preceding the string it indicates that it is a byte sequence which is equivalent to a normal string in Python 2.6+

http://docs.python.org/3/reference/lexical_analysis.html#literals

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