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

Question

Trying to decode some RLE text but I'm not sure how to do it via accessing the file, any ideas?

First I tried running the code with manually inputted string, worked fine, but whenever I try to access the file to read it and decode the RLE it doesn't seem to work.

def decode(m_str):
    number = ''
    ret_str = ''

    for index in range(len(m_str)):
        try:
            int(m_str[index])
            check = True
        except ValueError:
            check = False

        if check:
            number += m_str[index]
        else:
            ret_str += int(number)*m_str[index]
            number = ''

    return ret_str


f = open("RLE.txt", 'r')
read = f.read()

x = (read)
y = decode(x)
print(y)

If the content of the file is "5S4F8S" I expect it to output

SSSSSFFFFSSSSSSSS

Instead, I get the error:

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

Answer 1

Put in some basic debugging print commands:

def decode(m_str): number = '' ret_str = ''

for index in range(len(m_str)):
    try:
        int(m_str[index])
        check = True
    except ValueError:
        check = False

    print(index, check, number)
    if check:
        number += m_str[index]
    else:
        ret_str += int(number)*m_str[index]
        number = ''

return ret_str


f = open("RLE.txt", 'r')
read = f.read()

x = (read)
print(x, [ord(c) for c in x])
y = decode(x)
print(y)

Output:

5S4F8S
 [53, 83, 52, 70, 56, 83, 10]
0 True 
1 False 5
2 True 
3 False 4
4 True 
5 False 8
6 False 
Traceback (most recent call last):
  File "so.py", line 27, in <module>
    y = decode(x)
  File "so.py", line 16, in decode
    ret_str += int(number)*m_str[index]
ValueError: invalid literal for int() with base 10: ''

Your problem is quite simple: your input includes a non-printing character, such as the "newline" and the end of the input. That's not a legal item to convert.

To fix this, clean the input:

x = (read).strip()

This will allow you to get the desired output.

I'll leave the other improvements to you.