How to I check if a string contains only digits or "/" in Python?
digits, if-statement, python, string
Solution
There are many options, as showed here. A nice one would be list comprehensions.
Let's consider two strings, one that satisfies the criteria, other that doesn't:
>>> match = "123/456/"
>>> no_match = "123a456/"
We can check if a character of them matches by using `isdigit()` and comparation:
>>> match[0].isdigit() or match[0] == '/'
True
But we want to know if all chars match. We can get a list of results by using list comprehensions:
>>> [c.isdigit() or c == '/' for c in match]
[True, True, True, True, True, True, True, True]
>>> [c.isdigit() or c == '/' for c in no_match]
[True, True, True, False, True, True, True, True]
Note that the list of the non-matching string has `False` at the same position of the `'a'` char.
Since we want all chars to match, we can use the `all()` function. It expects a list of values; if at least one of them is false, then it returns false:
>>> all([c.isdigit() or c == '/' for c in match])
True
>>> all([c.isdigit() or c == '/' for c in no_match])
False
Bonus points
Put on a function
You would be better to put it on a function:
>>> def digit_or_slash(s):
... return all([c.isdigit() or c == '/' for c in s])
...
>>> digit_or_slash(match)
True
>>> digit_or_slash(no_match)
False
Generator expressions
Generator expressions tend to be more efficient:
>>> def digit_or_slash(s):
... return all(c.isdigit() or c == '/' for c in s)
...
But in your case it is probably negligible anyway.
What about `in`?
I would prefer to use the `in` operator, as below:
>>> def digit_or_slash(s):
... return all(c in "0123456789/" for c in s)
Note that this is only one of the options. Sadly, your problem fails this Zen of Python recommendation (`>>> import this`):
There should be one- and preferably only one -obvious way to do it.
But that's ok, now you can choose whatever you prefer :)
Problem
I am trying to check if a string contains only digits or "/", to use as a form of validation, however I cannot find and way to do both. ATM I have this: ``` if variable.isdigit() == False: ``` This works for the digits, but I have not found a way to check also for the slashes.