In Python functions are first class data members

Question

What does the following sentence mean ?

In Python functions are first class data members.

http://stackoverflow.com/questions/245192/what-are-first-class-objects — Mitch Wheat, Nov 18 '13 at 00:24
I think it's ambiguous. It could mean the sense of "first class function" or "functions are first class objects" — John La Rooy, Nov 18 '13 at 00:55

score 3 · Answer 1 · edited Nov 18 '13 at 00:27

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Specifically, this means the language supports passing functions as arguments to other functions, returning them as the values from other functions, and assigning them to variables or storing them in data structures.

edited Nov 18 '13 at 00:27

user2864740

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answered Nov 18 '13 at 00:25

gPxl

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I like this very simple definition. – user2864740 Nov 18 '13 at 00:29

evhen14 · Answer 2 · 2013-11-18T00:39:21.737

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It means that functions are represented as objects. You can easily pass them to other methods as parameters

def fun():
    print "Hi"
fun()

def take(f):
    f()

take(fun)

this will print "Hi" twice

Python is a hybrid language that supports both OO programming and functional programming and mostly first class functions make it functional language together with some other features such as tuples (read-only data types)

The key is that you can compose smaller functions to achieve larger goals

edited Nov 18 '13 at 00:39

answered Nov 18 '13 at 00:26

evhen14

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Your properties example doesn't have anything to do with functions being first-class. You can do that because functions by default have a `__dict__` attribute. You can easily create a `class` without a `__dict__`, but it's still a first-class object. – roippi Nov 18 '13 at 00:34
agree. edited by removing that claim and adding composition part – evhen14 Nov 18 '13 at 00:40

score 2 · Answer 3 · answered Nov 18 '13 at 00:27

In many languages first class data members are things like numbers, sequences (like arrays or strings) or objects (which can be thought if as sequences of things like numbers and other sequences). These are normally passed to functions where they might mutate or effect the execution or return value. In Python (and JavaScript, and many other languages actually) functions can be passed as arguments. This gives you tremendous flexibility in composing functions and it lets you create smaller more generic functions that take functions as arguments. This can be a by mind ending at first but as you use it you will wonder why other languages create these false distinctions.

In Python functions are first class data members

3 Answers3