How to pad a zero input in an argparser default?

Question

today = datetime.datetime.now()
day_before_date1 = datetime.date.today()-datetime.timedelta(days=2)
day_before_date = day_before_date1.strftime("%d")
print(day_before_date)  # 01 (is the output)

I have to use arg parser in python to take input for day. If I don't give any input it defaults to presentdate-2, which is 01.

parser.add_argument('number',type=int, help="Number represents date" , nargs='?' , default=day_before_date , const="num")

I have set default=int(day_before_date) but it still registers the input as 1 and not 01 when I print(args.number) I need 01 when i print(args.number).

You could use an f-string to print the value: `print(f"{day_before_data:02}")`. — Sean, Jun 02 '22 at 20:29
Does this answer your question? [How to pad zeroes to a string?](https://stackoverflow.com/questions/339007/how-to-pad-zeroes-to-a-string) — Macattack, Jun 02 '22 at 20:29
You have `type=int` in `parser.add_argument`. "01" is a string. — 001, Jun 02 '22 at 20:30
@Macattack ,No So when i will have days like 11 , 12 , it will add 0 to it as well and make it 011 , 012 — Yash, Jun 02 '22 at 20:31
similar to the f string you could use just the `%` formatting: `"%02d" % 2" -> 02` — Macattack, Jun 02 '22 at 20:35
The `zfill` method can be used as `'1'.zfill(2)` —> `'01'`. — S3DEV, Jun 02 '22 at 20:40

Alexander · Answer 1 · 2022-06-02T20:49:32.807

You can use the str.rjust method, this will guarantee that you will only ever have 2 characters so if it is 11 it will output '11' but if it is 3 it will output '03'

>>> a = 1
>>> str(a).rjust(2,"0")
"01"

another method is to use inline formating with f-strings.

>>> a = 1
>>> b = f"{a:02d}"
>>> b
"01"

Or you can use conditional statement (not recommended).

>>> a = 1
>>> b = '0' + str(a) if len(str(a)) == 1 else str(a)
>>> b
'01'

score 0 · Answer 2 · answered Jun 02 '22 at 20:55

You have two options. The first is to change what type your argument is in argparser:

parser.add_argument('number',type=str, help="Number represents date" , nargs='?' , default="01", const="num")
...
day_number_arg = int(args.number)
... # use `day_number_arg` wherever you would have used `args.number`
print(args.number)  # will print '01' if the default is used.

Here you take in a string and convert it to a number. You can print out the original argument as the string passed in, or the default.

Elsewise you can take your calculated value and use a format string:

day_number = 1
f"{day_number:02d}"

This says 'print two digits of day_number'. In this manner you can format the output, meaning you can use whatever your final value is. In general this would be the recommend method.

``` parser.add_argument('number',type=str, help="Number represents date" , nargs='?' , default="01", const="num") ... day_number_arg = int(args.number) ... # use `day_number_arg` wherever you would have used `args.number` print(args.number) ``` This gives 1 not ```01``` — Yash, Jun 03 '22 at 14:29

How to pad a zero input in an argparser default?

2 Answers2