Question

Whenever I try to run this code:

    #Open file
    f = open("i.txt", "r")
    line = 1

    #Detect start point
    def findstart( x ):
        length = 0
        epsilon = 7
        a = 3
        line_value = int(f.readline(x))
        if line_value == a:
            length = length + 1
            x = x + 1
            findend(x)
        elif line_value == epsilon:
            x = x + 2
            findstart(x)
        else:
            x = x + 1
            findstart(x)

    #Detect end point
    def findend(x):
        line_value = int(f.readline(x))
        if line_value == a:
            length = length + 1
            return ("Accept", length)
        elif line_value == epsilon:
            x = x + 2
            length = length + 2
            findend(x)
        else:
            x = x + 1
            length = length + 1
            findend(x)

    findstart(line)

I get this error code:

    Traceback (most recent call last):
  File "C:\Users\Brandon\Desktop\DetectSequences.py", line 39, in <module>
    findstart(line)
  File "C:\Users\Brandon\Desktop\DetectSequences.py", line 16, in findstart
    findend(x)
  File "C:\Users\Brandon\Desktop\DetectSequences.py", line 26, in findend
    line_value = int(f.readline(x))
    ValueError: invalid literal for int() with base 10: ''

Can anyone help me to figure out what’s wrong? It seems to me that it’s attempting to read an empty cell but I don’t know why that would be. The file I’m scanning currently only has two lines with each reading “3” so it should output a success but I can’t get past this error.

Answer 1

I’m not sure about your code, but the error message suggests that your file has an empty line in it and you’re trying to convert it to an int. For example, a lot of text files have an empty line at the end.

I’d suggest first checking your line before converting it:

line = ...
line = line.strip() # strip whitespace
if line: # only go on if the line was not blank
    line_value = int(line)