将函数输出打印分配给python中的变量 [英] Assign a function output prints to a variable in python

问题描述

我有一个函数(在某些项目中)可以打印结果.当我从命令行或另一个 python 项目调用它时，它会在终端上打印输出.但我想将所有打印结果存储在一个变量中，如下所示:

output = function_name(function_args)

而不是在终端上打印结果，我想将它们存储在 output 变量中.此外，主函数返回一些东西(只是一个数字作为状态)作为结果，我不想要那个数字.

解决方案

您可以通过重新绑定 sys.stdout 来实现:

<预><代码>>>>定义 foo():...打印('土豆')...>>>导入系统，io>>>sys.stdout = io.StringIO()>>>富()>>>val = sys.stdout.getvalue()>>>sys.stdout = sys.__stdout__ # 恢复原始标准输出>>>打印(val)土豆

要获得更好的方法，请考虑编写上下文管理器.如果您使用的是 Python 3.4+，则已经为您编写.

<预><代码>>>>从 contextlib 导入 redirect_stdout>>>f = io.StringIO()>>>使用 redirect_stdout(f):... foo()...>>>打印(f.getvalue())土豆

在您能够修改函数本身的情况下，允许输出流的依赖注入可能更清晰(这只是传递参数"的一种奇特方式):

def foo(file=sys.stdout):打印('土豆'，文件=文件)

I have a function (in some project) that it prints the result.when I call it from the command line or in another python project, it prints the output on the terminal. But I want to store all the print result in a variable, something like this:

output = function_name(function_args)

and instead of printing the results on the terminal I want to store them in the output variable. also, the main function returns something(just a number as the status) as the result which i do not want that number.

解决方案

You can do this by rebinding sys.stdout:

>>> def foo():
...     print('potato')
... 
>>> import sys, io
>>> sys.stdout = io.StringIO()
>>> foo()
>>> val = sys.stdout.getvalue()
>>> sys.stdout = sys.__stdout__  # restores original stdout
>>> print(val)
potato

For a nicer way to do it, consider writing a context manager. If you're on Python 3.4+, it's already been written for you.

>>> from contextlib import redirect_stdout
>>> f = io.StringIO()
>>> with redirect_stdout(f):
...     foo()
... 
>>> print(f.getvalue())
potato

In the case that you are able to modify the function itself, it may be cleaner to allow a dependency injection of the output stream (this is just a fancy way of saying "passing arguments"):

def foo(file=sys.stdout):
    print('potato', file=file)

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