"print >>" 在 python 中做什么？

Question

我必须将 python 2 中的代码翻译成 python 3，我无法理解 print >> 的作用以及我应该如何在 [=16= 中编写它] 3.

print >> sys.stderr, '--'
print >> sys.stderr, 'entrada1: ', entrada1
print >> sys.stderr, 'entrada2: ', entrada2
print >> sys.stderr, '--'

Answer 1

>> sys.stderr 部分使 print 语句输出到 stderr 而不是 Python 中的 stdout 2.

引用documentation：

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.

在Python 3中使用print()函数的file参数：

 print("spam", file=sys.stderr)

Answer 2

要将这些从 Python 2 转换为 Python 3，请更改：

print >>sys.stderr, 'Hello'

至：

print('Hello', file=sys.stderr)

Answer 3

用于打印到 stderr 便笺

sys.stderr.write()

可跨版本移植，但与print不同，您需要添加换行符；例如

import sys

errlog = sys.stderr.write
errlog("an error message\n")

"print >>" 在 python 中做什么？

What does "print >>" do in python?

python

python-2.x

python-3.x