Python: Map calling a function not working

Question

Map not calling the function being passed.

class a:
    def getDateTimeStat(self,datetimeObj):
        print("Hello")

if __name__ == "__main__":
    obj = a()
    print("prog started")
    data = [1,2,3,4,5]
    b = list(map(obj.getDateTimeStat,data))

Expected op on a new line: Hello Hello Hello Hello Hello

Any help will be appreciated....

Answer 1

In Python 3, map values are evaluated lazily. That is, each value is only computed when it's needed. You'll find that regardless of what function you use, it won't get called until you ask for the value of that item in the mapped result, whether by using next() or some other way.

To get what you want, you can do this:

>>> b = map(obj.getDateTimeStat,data)
>>> next(b)
Hello
>>> next(b)
Hello
>>> next(b)
Hello
>>> next(b)
Hello
>>> next(b)
Hello
>>> next(b)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
StopIteration

Or this:

>>> b = list(map(obj.getDateTimeStat,data))
Hello
Hello
Hello
Hello
Hello

Or a variety of other things.