python - Python 中的双大于号

Question

我正在查看一些 Python 源代码，当我遇到这个时:

print >> sys.stderr, __doc__

>>是什么意思？我以前从未见过这样的语法。

Answer 1

请参阅 Python 2.7 docs 中的“print chevron”说明:

print also has an extended form, defined by the second portion of the syntax described above. This form is sometimes referred to as “print chevron.” In this form, the first expression after the >> must evaluate to a “file-like” object, specifically an object that has a write() method as described above. With this extended form, the subsequent expressions are printed to this file object. If the first expression evaluates to None, then sys.stdout is used as the file for output.

特殊语法在 Python 3 中消失了，因为 print 从语句转换为函数。