CODEWITHSUNDEEP
python
Cube.
Cube.

Reputation: 513

Check if required variable has been passed

I have a function which requires a parameter (whateverName(n)) to be passed in. I want to check if the parameter was indeed passed and if it wasn't, I want to display a prompt asking what the desired parameter should be (n = int(raw_input(...))). Any ideas how this can be done (note: I'm a rookie in Python)?

Upvotes: 3

Views: 2874

Answers (2)

RobertB
RobertB

Reputation: 1929

Try:

def whatever(n=None):
    if n is None:
        n = input("Enter n:")
    print(n)

Upvotes: 0

Kevin
Kevin

Reputation: 76194

Give n a default value of None, and check for it in the function body.

>>> def frob(n=None):
...     if n is None:
...             n = int(raw_input("Please enter a value:"))
...     return n**2 + n
...
>>> frob(23)
552
>>> frob()
Please enter a value:42
1806

Of course, this means that the user will be unable to call frob(None) even if he's sure that's the value he wants n to have. But in this particular case, frob can only successfully handle integers anyway, so the user shouldn't need to call frob(None) anyway.

Upvotes: 5

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