I am getting value error in python program-CodePudding

t = int(input())
for _ in range(t):
    n = input()
    for i in range(len(n)):
        first = n[:i]
        second = n[i:]
        print(type(first))
        print(type(int(first)))

Why I am getting ValueError: invalid literal for int() with base 10: ''

Output: output

CodePudding user response：

ValueError: invalid literal for int() with base 10: ''

As the error says, you entered an empty value (''), that the built-in function int isn't able to convert.

If you want to check if t is acceptable (an integer) you can use .isdigit:

>>> '1'.isdigit()
True
>>> ''.isdigit()
False
>>> 'Hello1'.isdigit()
False

Or maybe use a try/except block:

try:
    t = int(input())
except ValueError:
    print("Error, your input wasn't a number")

As your screenshot shows, the error gets raised at:

print(type(int(first)))

but the reason is the same, you can solve it with the try/except block above.

try:
    print(type(int(first)))
except ValueError:
    pass # Simply do nothing, since an empty element of n was reached

CodePudding user response：

For purposes of debugging, let's just focus on a single iteration and assign a reasonable value to n that represents the sort of thing you expect the user to input(). (When people ask you for an "MRE", this is the type of thing they mean -- a small piece of code that you can run to immediately demonstrate the problem.)

n = "12345"
for i in range(len(n)):
    first = n[:i]
    second = n[i:]
    print(type(first))
    print(type(int(first)))

It breaks here:

    print(type(int(first)))
ValueError: invalid literal for int() with base 10: ''

Why is that? Well, let's do a little more printing:

    print(f"first = n[:{i}] = {repr(first)}")

gets us:

first = n[:0] = ''

And indeed, the slice n[:0] is an empty string, which you can't convert to an int. What you probably want to do is reduce your range so that it starts at 1 instead of 0:

n = "12345"
for i in range(1, len(n)):
    first = n[:i]
    second = n[i:]
    print(f"first = n[:{i}] = {repr(first)}")
    print(f"second = n[{i}:] = {repr(second)}")

prints:

first = n[:1] = '1'
second = n[1:] = '2345'
first = n[:2] = '12'
second = n[2:] = '345'
first = n[:3] = '123'
second = n[3:] = '45'
first = n[:4] = '1234'
second = n[4:] = '5'