python - How do I check for an integer in a text file?

Question

This question already has answers here: question from:https://stackoverflow.com/questions/65949072/how-do-i-check-for-an-integer-in-a-text-file

Answer 1

Your approach is a good starting point. Depending on exactly what sort of file you are reading and its contents (which isn't specified), there are a few approaches which may work:

1. Before calling your function with an integer value, convert it to a string with str:

check_if_string_in_file(file_name, str(123))

Note that this approach falls short if e.g. your file has a line like "12345", as '123' in '12345' is true. You can resolve this by using a more strict check (instead of just in).

2. If you know that all the lines in your file will just be numbers, you can convert the line to number after reading it in using the int function:

def check_if_string_in_file(file_name, number_to_search):
    with open(file_name, 'r') as read_obj:
        for line in read_obj:
            line_as_int = int(line.strip())
            if number_to_search == line_as_int:
                return True
    return False

If you plan to do several such checks, it may make sense to read the whole file into a list in one shot and then check for the target in the list.