Converting a string into an integer

Question

I am trying to write a program that determines leap years. My problem is that I cannot convert the year variable into an integer. I attempt to parse the variable in the try statement. the error I am receiving is

line 19, in divide_by_4
if (year%4) == 0:
TypeError: not all arguments converted during string formatting

My code is below: and the file I imported in only had 1804 in it

def is_year(year):
    '''determine if the input year can be converted into an integer'''
    try:
        int(year)
        return year
    except ValueError:
        print("current year is not a year")

def divide_by_4(year):
    if (year%4) == 0:
        return True

def divide_by_100(year):
    if (year % 100) == 0:
        return True

def divide_by_400(year):
    if (year % 400) == 0:
        return True


def leap_year(year):
    if is_year(year):
        if divide_by_4(year):
            if divide_by_100(year):
                if divide_by_400(year):
                    return True
            else:
                if divide_by_400(year):
                    return True


def main():

    input_file = input("Enter the file input file name: ")
    output_file = input("Enter the output file name: ")

    try:
        file_in = open(input_file, 'r')
    except IOError:
        print("The input file could not be opened. The program is ending")

    try:
        file_out = open(output_file, 'w')
    except IOError:
        print("The output file could not be opened. The program is ending")

    for years in file_in:
        if leap_year(years):
            file_out.write(years)
    file_in.close()
    file_out.close()

main()

Piotr Sobczyk · Accepted Answer · 2014-09-11 06:43:31Z

1

How about:

def divide_by_4(year):
    if (int(year) % 4) == 0:
        return True

Justification: In is_year function you don't actually convert String to int. Instead you just check if it is possible to convert it. That's why you need to make actual conversion ( int(year) ) before you use year as integer.

The same problem will occur in divide_by_100.

edited Sep 11, 2014 at 6:43

answered Sep 11, 2014 at 6:38

Piotr Sobczyk

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Comments

Fortune Zhang · Accepted Answer · 2014-09-11 08:08:32Z

0

when you read data from file, the data's type is string , so you can't use year % 4. you can do like that:

def leap_year(year):
    if is_year(year):
        year = int(year)
        ......

then do it

answered Sep 11, 2014 at 8:08

Fortune Zhang

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