CODEWITHSUNDEEP
pythonlambda
M. Bremer
M. Bremer

Reputation: 41

Python specify lambda arguments as a function argument

Is there any possibility to specify how many arguments a lambda as a function argument can take?

For example:

def func(k=lambda x:return x**2):
   return k

Could i specify, if k is not the standard lambda, that k is supposed to take exactly one argument?

Max

Upvotes: 2

Views: 447

Answers (1)

Holt
Holt

Reputation: 37606

You could do something like this using inspect.getargspec:

import inspect
def func (k = lambda x: x ** 2):
    if not callable(k) or len(inspect.getargspec(k).args) != 1:
        raise TypeError('k must take exactly one argument.')
    # Do whatever you want

Note that the above will miserably fail with something like (while it shouldn't):

func (lambda x, y = 8: x + y)

...so you will need something a bit more complicated if you want to handle this case:

import inspect
def func (k = lambda x: x ** 2):
    if not callable(k):
        raise TypeError('k must be callable.')
    argspec = inspect.getfullargspec(k)
    nargs = len(argspec.args)
    ndeft = 0 if argspec.defaults is None else len(argspec.defaults)
    if nargs != ndeft + 1:
        raise TypeError('k must be callable with one argument.')
    # Do whatever you want

Upvotes: 6

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