CODEWITHSUNDEEP
pythonstringdatedatetime
franchyze923
franchyze923

Reputation: 1200

How to ensure user input date is in correct format

I need to ensure the user enters the date in the following format -

12/23/1993

If it's a single digit month or day, I need a leading zero included.

I need 02/04/1998 not 2/4/1998

How can I ensure that leading zeros or 2 digits are present?

This is what I have so far 

from datetime import datetime


def validate_date(d):
    try:
        datetime.strptime(d, '%m/%d/%Y')
        return True

    except ValueError:
        return False


print validate_date('02/26/2009')  # prints False

However, this will print true even if a single digit is entered for month/day.

Upvotes: 2

Views: 7247

Answers (4)

Viraj Indasrao
Viraj Indasrao

Reputation: 27

Whatever user input is, you can convert it to your required format.

>>> date_string = '2/4/1998'
>>> datetime.datetime.strptime(date_string, '%m/%d/%Y').strftime('%m/%d/%Y')
'02/04/1998'

and to ensure user entered format as follows

def validate_date_format(date_string):
    try:
        datetime.datetime.strptime(date_string, '%m/%d/%Y')
    except ValueError:
        raise ValueError("Date format should be MM/DD/YYYY")

Upvotes: 1

Alter
Alter

Reputation: 3464

Not to over engineer... you can probably just check the length of the string. This will work for years between 1000-9999

from datetime import datetime

def validate_date(d):
    try:
        if len(d) == 10: 
            datetime.strptime(d, '%m/%d/%Y')
            return True
        else: return False

    except ValueError:
        return False

print(validate_date('2/26/1000'))

Upvotes: 4

Scott Mermelstein
Scott Mermelstein

Reputation: 15397

I am not aware of a way to force strptime to validate that there is a leading 0. As you said, it's happy with both 2/4/1998 and 02/04/1998. I don't know of any way to do this other than a regular expression:

import re
regex = r'\d{2}/\d{2}/\d{4}'
if re.match(d):
    # then it matches the syntax you want

But you still want to use strptime to validate the input, so you don't get some mess like '99/99/0123'.

When you put it all together, you'd need something like this:

from datetime import datetime
import re

def validate_date(d):
    try:
        regex = r'\d{2}/\d{2}/\d{4}'
        if re.match(d):
            datetime.strptime(d, '%m/%d/%Y')
            return True

    except ValueError:
        return False

    return False

If you're not familiar with regexes, this is a relatively simple one. The leading r tells python this is a raw string, and it shouldn't process backslashes. \d means any digit, and the {2} and {4} says that it should repeat (any digit) 2 and 4 times respectively.

Upvotes: 0

Jacobm001
Jacobm001

Reputation: 4539

I'd handle this with a loop to get input from the user.

  1. Prompt the user for a value (let them know how it should be formatted) and then try to cast it like you're doing.

  2. If the cast succeeds then you break the loop and continue. If it fails...

  3. You catch the error and display the message about an invalid format and repeat step 1. Loop until you get a valid value.

good_value = false
value = ""

while good_value == false:
    value = input("Insert Date in format...")

    try:
        datetime.strptime(d, '%m/%d/%Y')
        good_value = true

    except ValueError:
        print("Error: Date format invalid.")

Upvotes: 0

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