How to check that variable is a lambda function
lambda, python, types
Solution
You need to use `types.LambdaType` or `types.FunctionType` to make sure that the object is a function object like this
x = lambda d:d*d
import types
print type(x) is types.LambdaType
# True
print isinstance(x, types.LambdaType)
# True
and then you need to check the name as well to make sure that we are dealing with a lambda function, like this
x = lambda x: None
def y(): pass
print y.__name__
# y
print x.__name__
# <lambda>
So, we put together both these checks like this
def is_lambda_function(obj):
return isinstance(obj, types.LambdaType) and obj.__name__ == "<lambda>"
As @Blckknght suggests, if you want to check if the object is just a callable object, then you can use the builtin `callable` function.
Problem
I'm working on a project, which contains several modules. Simplifying the problem, there is some variable x. Sometimes it may be int or float or list. But it may be a lambda function, and should be treated in different way. How to check that variable x is a lambda? For example ``` >>> x = 3 >>> type(x) <type 'int'> >>> type(x) is int True >>> x = 3.4 >>> type(x) <type 'float'> >>> type(x) is float True >>> x = lambda d:d*d >>> type(x) <type 'function'> >>> type(x) is lambda File "<stdin>", line 1 type(x) is lambda ^ SyntaxError: invalid syntax >>> type(x) is function Traceback (most recent call last): File "<stdin>", line 1, in <module> NameError: name 'function' is not defined >>> ```