函数不会从"for"循环返回所有结果 [英] Function doesn't return all results from 'for' loop

问题描述

我已经做了一个简单的功能，可以根据您决定使用的编号来打印时间表表.由于对语言的基本了解，我遇到的问题是为什么它只返回第一个循环，而没有返回其他循环.

I've made a simple function to print out a times table chart depending on the number you decide to run with. The problem I'm having due to my basic understanding of the language is why it only returns the first loop and nothing else.

def timestables(number):
  for a in range(1, number+1):
    b = a*a
    c = a
    return (str(c) + " * " + str(c) + " = " + str(b))

print(timestables(5))

我得到了答案..

1 * 1 = 1

我试图通过使用print而不是return来纠正此问题，但这最终也会导致显示None(无).

I've tried to rectify this issue by using print instead of return but this ultimately results with a None appearing as well.

def timestables(number):
  for a in range(1, number+1):
    b = a*a
    c = a
    print (str(c) + " * " + str(c) + " = " + str(b))

print(timestables(5))

我得到了答案..

1 * 1 = 1
2 * 2 = 4
3 * 3 = 9
4 * 4 = 16
5 * 5 = 25
None

如何从for循环中返回所有给定的结果，以避免None错误?

How can I return all given results from the for loop to avoid a None error?

推荐答案

您正在return进入for循环内-函数一旦遇到return语句，就会立即停止执行.

You're returning inside the for loop - and functions stop execution immediately once they hit a return statement.

要解决此问题，您可以使用列表存储这些值，然后返回该列表.

To work around this, you can use a list to store those values, and then return that list.

def timestables(number):
    lst = []
    for a in range(1, number+1):
        b = a*a
        c = a
        lst.append(str(c) + " * " + str(c) + " = " + str(b))
    return lst

请注意，您应该使用 字符串格式 来构建字符串，就像这样.

As a side note, you should use string formatting to build the string, like so.

lst.append('{a} * {a} = {b}'.format(a=a, b=a*a))

现在，我们可以摆脱所有这些中间变量(b和c)，并且可以使用

Now we can get rid of all those intermediate variables (b and c), and we can use a list comprehension instead.

def timestables(number):
    return ['{a} * {a} = {b}'.format(a=a, b=a*a) for a in range(1, number+1)]

如果您不希望函数返回列表，而是返回多行字符串，则可以使用

If you don't want the function to return a list, but a multi-line string, you can use str.join:

def timestables(number):
    return '\n'.join('{a} * {a} = {b}'.format(a=a, b=a*a) for a in range(1, number+1))

现在我们可以测试该功能了:

Now we can test the function:

>>> print(timestables(5))
1 * 1 = 1
2 * 2 = 4
3 * 3 = 9
4 * 4 = 16
5 * 5 = 25

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