“打印"和“打印"之间的正式区别是什么?和“返回"? [英] What is the formal difference between "print" and "return"?

问题描述

假设我定义了一个简单的函数，它将显示传递给它的整数:

Lets say I define a simple function which will display an integer passed to it:

def funct1(param1):
    print(param1)
    return(param1)

输出将是相同的，但我知道当在函数中使用 return 语句时，输出可以再次使用.否则不能使用 print 语句的值.但我知道这不是正式的定义，谁能给我一个好的定义?

the output will be the same but and I know that when a return statement is used in a function the output can be used again. Otherwise the value of a print statement cannot be used. But I know this is not the formal definition, Can anyone provide me with a good definition?

推荐答案

截然不同的事情.想象一下，如果我有这个 python 程序:

Dramatically different things. Imagine if I have this python program:

#!/usr/bin/env python

def printAndReturnNothing():
    x = "hello"
    print(x)

def printAndReturn():
    x = "hello"
    print(x)
    return x

def main():
    ret = printAndReturn()
    other = printAndReturnNothing()

    print("ret is: %s" % ret)
    print("other is: %s" % other)

if __name__ == "__main__":
    main()

您希望输出什么?

hello
hello
ret is : hello
other is: None

<小时>

为什么?

为什么?因为 print 接受它的参数/表达式并将它们转储到标准输出，所以在我编写的函数中，print 将输出 x 的值，这是hello.

---

Why?

Why? Because print takes its arguments/expressions and dumps them to standard output, so in the functions I made up, print will output the value of x, which is hello.

• printAndReturn 会将 x 返回给方法的调用者，所以:

• printAndReturn will return x to the caller of the method, so:

ret = printAndReturn()

ret 将与 x 具有相同的值，即 "hello"

ret will have the same value as x, i.e. "hello"

• printAndReturnNothing 不返回任何内容，因此:

• printAndReturnNothing doesn't return anything, so:

other = printAndReturnNothing()

other 实际上变成了 None 因为这是 Python 函数的默认返回值.Python 函数总是返回一些东西，但如果没有声明 return，函数将返回 None.

other actually becomes None because that is the default return from a python function. Python functions always return something, but if no return is declared, the function will return None.

通过 Python 教程将向您介绍这些概念:http://docs.python.org/tutorial

Going through the python tutorial will introduce you to these concepts: http://docs.python.org/tutorial

以下是 Python 教程中有关函数的一些内容:http://docs.python.org/tutorial/controlflow.html#defining-functions

Here's something about functions form python's tutorial: http://docs.python.org/tutorial/controlflow.html#defining-functions

这个例子和往常一样，展示了一些新的 Python 特性:

This example, as usual, demonstrates some new Python features:

return 语句返回一个函数的值.没有表达式参数的 return 返回 None.从函数的末尾脱落也会返回 None.

The return statement returns with a value from a function. return without an expression argument returns None. Falling off the end of a function also returns None.

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