CODEWITHSUNDEEP
pythonwhile-loop
Arthur
Arthur

Reputation: 35

Python: Writing to file using while loop fails with no errors given

I am attempting to collect only certain type of data from one file. After that the data is to be saved to another file. The function for writing for some reason is not saving to the file. The code is below:

def reading(data):
file = open("model.txt", 'r')
while (True):
    line = file.readline().rstrip("\n")
    if (len(line) == 0):
        break
    elif (line.isdigit()):
        print("Number '" + line + "' is present. Adding")
file.close()
return None

def writing(data):
    file = open("results.txt", 'w')
    while(True):
        line = somelines
        if line == "0":
            file.close()
            break
        else:
            file.write(line + '\n')
    return None

file = "model.txt"
data = file
somelines = reading(data)
writing(data)

I trying several things, the one above produced a TypeError (unsupported operand). Changing to str(somelines) did solve the error, but still nothing was written. I am rather confused about this. Is it the wrong definition of the "line" in the writing function? Or something else?

Upvotes: 1

Views: 230

Answers (2)

ChrisOram
ChrisOram

Reputation: 1434

Assuming you want one reading function which scans the input file for digits, and one writing file which writes these digits to a file until the digit read is 0, this may help:

def reading(file_name):
    with open(file_name, 'r') as file:
        while True:
            line = file.readline().rstrip("\n")
            if len(line) == 0:
                break
            elif line.isdigit():
                print("Number '" + line + "' is present. Adding")
                yield line

def writing(results_file, input_file):
    file = open(results_file, 'w')
    digits = reading(input_file)
    for digit in digits:
        if digit == "0":
            file.close()
            return
        else:
            file.write(digit + '\n')
    file.close()

writing("results.txt", "model.txt")

Upvotes: 1

Red
Red

Reputation: 27567

See this line in your writing function:

            file.write(line + '\n')

where you have

        line = somelines

and outside the function you have

somelines = reading(data)

You made your reading function return None. You cannot concat None with any string, hence the error.

Upvotes: 2

Related Questions