不使用局部变量“行”值？

Question

When this script is used without the 'def main():' then the error doesn't appear but when it is inside this function the error seems to appear.

I have had a look into what I could find online regarding this issue but none of them can directly relate.

Sorry had to fix the code

def main():
    count = sum(1 for line in open('text.txt'))

Answer 1

Note that this isn't an error, it's a warning. You can ignore it if you want to, but personally I also like removing warnings.

The conventional way to signal to both readers and tools that a variable is intentionally unused is to name it _ (a single underscore), eg

def main():
    count = sum(1 for _ in open('text.txt'))

In PyCharm, prefixing with an underscore (eg _line ) also works if you want readers to know what the ignored variable is.