How to format a date in python

Question

Im currently doing a program in which stores user information such as their forename, surname and birth date. I'm not very experienced with advanced python functions and I've tried declaring the Birth date as a string value, but this leads to issues where literally any input can be provided, such as "24/05/98" or "24/05/1998".

How can i make the input only work with the format "DD/MM/YYYY"?

Answer 1

In general, it's not a great idea to let the user input structured data like this where "literally any input can be provided".

But the python-dateutil package does a good job trying to accommodate.

from dateutil import parser

s1 = "24/05/98"
s2 = "24/05/1998"
s3 = "05/24/1998"

dt1 = parser.parse(s1)
dt2 = parser.parse(s2)
dt3 = parser.parse(s3)

print dt1           # 1998-05-24 00:00:00
print dt2           # 1998-05-24 00:00:00
print dt3           # 1998-05-24 00:00:00
print dt1 == dt2    # True
print dt1 == dt3    # True

Obviously, this niceness breaks down when it can't figure out the input, for example what order the month and date are in the string:

s4 = "1/2/15"       # Feb 1, 2015 in D/M/Y
s5 = "2/1/15"       # Feb 1, 2015 in M/D/Y

dt4 = parser.parse(s4)
dt5 = parser.parse(s5)

print dt4           # 2015-01-02 00:00:00
print dt5           # 2015-02-01 00:00:00
print dt4 == dt5    # False

---

Edit: Per your comment, if you know the format of the data, you can use strptime .

If the input cannot be parsed successfully, given the pattern you provide (in this case, %d/%m/%Y or DD/MM/YYYY ), a ValueError will be raised.

from datetime import datetime

s1 = "24/05/1998"
s2 = "05/24/1998"
s3 = "24/05/98"

for s in [s1, s2, s3]:
    try:
        dt = datetime.strptime(s, "%d/%m/%Y")
        print(dt)
    except ValueError:
        print("Failed to parse: %s" % s)

Output:

1998-05-24 00:00:00           # Parse successful -- dt contains the datetime object
Failed to parse: 05/24/1998   # Parse failed
Failed to parse: 24/05/98     # Parse failed

Answer 2

Try this code, i hope it will solve your problem.

from time import strptime

date = raw_input("Please enter a date in DD/MM/YYYY format: ")
try:
    parsed = strptime(date, "%d/%m/%Y")
except ValueError as e:
    print "Please retry: {0}".format(e)
#Do your work...