你如何定义一个for循环？

Question

How do you define a variable in a for loop?

def test():
    for i in range(1,999):
        do this thing blah blah blah
def another_function(parameter):
    test() # runs the function test()

But when I run the if __name__ == __main__ , it asks for me to define the variable i .

if __name__ == __main__:
    another_function(parameter = i # define i)

One thing I've tried is to define i using its own for loop:

if __name__ == __main__:
    i = i in range(1, 999)

    another_function(parameter = i)

And that doesn't work.

Should I try another way that isn't if __name__ == __main__ or is there even a way to define i ?

Answer 1

A few basic for loop examples in python:

def for_loop_example_1():
    for i in range(0,10):
        print("Hello world")

def for_loop_example_2():
    sum = 0
    for i in range(0,10):
        sum+=i
    return sum

if __name__ =='__main__':
    for_loop_example() #this prints "Hello world" 10 times
    print("\n") #Adding a line break
    sum = for_loop_example_2
    print(sum) #This prints 45 i.e sum of numbers from 0 till 10

Answer 2

You are trying to pass a parameter to the function. The value of the parameter should be i . But, what is the value of i ? Before using i , you should specify its value.

i = i in range(1, 999) # This will only make the value of i as True and pass parameter variable with a value of True

Answer 3

If I understood well, here:

if __name__ == __main__:
    another_function(parameter = i # define i)

you are trying to set parameter as i , but i is a variable, so you have to create it first and allocate a value. That's way it is asking to define i . This would work:

if __name__ == __main__:
        i = 2
        another_function(parameter = i # define i)

When you try to do: i = i in range(1, 999) , I guess you are trying to create a for loop in one line, but that's wrong. You need square brackets. And calling the function inside the brackets.

[another_function(parameter = i) for i in range(1, 999)]

This would run the for loop, assignt i = 1, call another_function, reassign i = 2, recall the function, and so on.

Answer 4

Since parameter isn't used, you can fix this code by removing it:

def test():
    for i in range(1, 999):
        # do this thing blah blah blah

def another_function():
    test() # runs the function test()

if __name__ == __main__:
    another_function()

Since i is defined inside the for loop in test there is no way (and no reason) to refer to it outside of that function, and since parameter wasn't used in your original code there's no reason to need to come up with a value (like i ) to pass into it from your __main__ block.