第8行：ValueError：int（）以10为底的无效文字：“'

Question

I'm a beginner programmer. I want to write a program that gives me the maximum product of all the products of 4-adjacent digits in an input number. So, if the input is "12345678" Possible selections are 1234, 2345,3456,4567,5678 and the largest product is 5*6*7*8.

My code:

number = str(input("Enter a number:"))
i = 0
L = []
while (i!=len(number)-3):
    a = int(number[i])
    b = int(number[i+1])
    c = int(number[i+2])
    d = int(number[i+3])
    product = a*b*c*d
    L.append(product)
    i = i+1
print(L)
print(number)
print(max(L))

I need to apply this to a 1000-digited number. My code works for 8-digited input number and gave an answer for a 500-digited number.

But I tried it with a 600-digited number and it throws this error.

I understand ValueError is an error that appears when the argument given to a function call has correct type, but inappropriate value. There are also examples of when the user gives a string "Alexander" as input in code Eg: int(input("Enter a number"))

the error is for '' an empty string that cannot be converted to an integer. But I cannot understand where/why the empty string was formed.

I have read a few other answers of this Error type, but all involve code that use features of Python I am NOT familiar with and hence cannot understand. I'm just a beginner! So, please help!

And apologies for breaking any rules laid out with regards to question formation!

Answer 1

You've got a space there, not an empty string. Most likely, you just hit the space bar at the end of your input, and Python can't convert that to an integer. You can either just ensure that you don't leave a space at the end, or do some checking of your input (eg, add a line number = number.strip() to remove any trailing whitespace).

Answer 2

Validate your input as numeric, and strip any whitespace:

number ='123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890'

def foo(number):
    number = number.strip()
    if number.isdigit():
        i = 0
        L = []
        while (i in range(len(number)-3)):
            a = int(number[i])
            b = int(number[i+1])
            c = int(number[i+2])
            d = int(number[i+3])
            product = a*b*c*d
            L.append(product)
            i = i+1
        return max(L)

This functions should return a None if user has provided invalid input (eg, "Alexander"), this should avoid the error you describe:

There are also examples of when the user gives a string "Alexander" as input in code Eg: int(input("Enter a number"))

You can also simplify this using a generator statement for a set of only the unique results:

def foo2(number):
    number = number.strip()
    if number.isdigit():
        return max({int(number[i]) * int(number[i+1]) * int(number[i+2]) * int(number[i+3]) for i in range(len(number)-3)})