Python TypeError：“NoneType”类型的对象没有 len()

Question

I am getting an error from this code:

def make_int(var):
    if len(var) != 0:
        var = int(var)
    return var

error:

TypeError: object of type 'NoneType' has no len()

How do i fix this?

Answer 1

It looks like you are trying to avoid a ValueError when calling int(var) , but failing to anticipate all the things that could cause one. Don't try; in this case, you are passing an argument that doesn't raise a ValueError anyway ( int(None) raises a TypeError instead). Just catch the exception and return var if it happens.

def make_int(var):
    try:
        return int(var)
    except Exception:
        return var

Answer 2

use this snippet

def make_int2(var):
    if isinstance(var, str) and var.isdigit():
        return int(var)
    return None