function tests haven't gone as expected(part of AoC day4)

user_13892424 0
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I wrote a function that checks if data is correct. Requirements are as follows:

byr-(Birth Year) - four digits; at least 1920 and at most 2002.

iyr (Issue Year) - four digits; at least 2010 and at most 2020.

eyr (Expiration Year) - four digits; at least 2020 and at most 2030.

def check_byr_iyr_eyr(line):
    statement = True
    if line[:3] == "byr":
        if (len(line[line.index(':')+1:]) != 4 or
        1920 > int(line[line.index(':')+1:]) > 2002 ):
            statement = False
    elif line[:3] == "iyr":
        if (len(line[line.index(':')+1:]) != 4 or
        2010 > int(line[line.index(':')+1:]) > 2020 ):
            statement = False
    elif line[:3] == "eyr":
        if (len(line[line.index(':')+1:]) != 4 or
        2020 > int(line[line.index(':')+1:]) > 2030 ):
            statement = False
    return statement


list = ['byr:1919', 'iyr:2010', 'eyr:2021', 'iyr:2019', 'iyr:1933',
        'byr:1946', 'iyr:1919', 'eyr:2005']

for i in list:
    print(check_byr_iyr_eyr(i))

'''
    expected result:
        False
        True
        True
        True
        False
        True
        False
        False
'''

and results of checking provided samples should be like in that multi-line comment "expected results", but unfortunately a result is always True.

I don't know what I'am doing wrong - conditions seems good to me...

if-statement function python
3 Answers

Consider this line:

1920 > val > 2002

It is the same result as:

val < 1920 and val > 2002

It means that val is both less than 1920, and greater than 2002, which can never be true.

user_6740390

An elegant solution, using too many if statements is not DRY (don't repeat yourself):

def check_byr_iyr_eyr(line):
    # split the string on the colon to get the two parts
    prefix, year = line.split(':')
    # getting around python's lack of case statements with a dictionary
    cases = {
        'byr': {'min': 1920, 'max': 2002},
        'iyr': {'min': 2010, 'max': 2020},
        'eyr': {'min': 2020, 'max': 2030},
    }
    # get the corresponding min and max and check if the year is inclusively between them
    # (note the <= instead of <)
    return cases[prefix]['min'] <= int(year) <= cases[prefix]['max']


data = ['byr:1919', 'iyr:2010', 'eyr:2021', 'iyr:2019', 'iyr:1933',
        'byr:1946', 'iyr:1919', 'eyr:2005']

for i in data:
    print(check_byr_iyr_eyr(i))

Output:

False
True
True
True
False
True
False
False
user_124424790

There are two problems with your function:

  1. Instead of doing complicated string slicing to check what type it is, just do string in line. It's much simpler and readable.

  2. The expression 5 > x > 7, as wim mentioned, is equivalent to an and statement. Since x cannot be both smaller than 5 and greater than 7, this is never True. Do x > 7 or x < 5 instead.

Below is the corrected code which has the correct output:

def check_byr_iyr_eyr(line):
    statement = True
    if "byr" in line:
        if (len(line[line.index(':')+1:]) != 4 or
        int(line[line.index(':')+1:]) > 2002 or 
        int(line[line.index(':')+1:]) < 1920):
            statement = False
    elif "iyr" in line:
        if (len(line[line.index(':')+1:]) != 4 or
        int(line[line.index(':')+1:]) > 2020 or 
        int(line[line.index(':')+1:]) < 2010):
            statement = False
    elif "eyr" in line:
        if (len(line[line.index(':')+1:]) != 4 or
        int(line[line.index(':')+1:]) > 2030 or
        int(line[line.index(':')+1:]) < 2020):
            statement = False
    return statement


list = ['byr:1919', 'iyr:2010', 'eyr:2021', 'iyr:2019', 'iyr:1933',
        'byr:1946', 'iyr:1919', 'eyr:2005']

for i in list:
    print(check_byr_iyr_eyr(i))

'''
    expected result:
        False
        True
        True
        True
        False
        True
        False
        False
'''

Check out Tenacious B's answer for a much more elegant solution!

user_137369520
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