Calling a variable as a function

Question

def f(x):
    def g():
        x='abc'
        print('x=',x)
    def h():
        z=x
        print('z=',z)
    x=x+1
    print('x=',x)
    h()
    g()
    print('x=',x)
    return g
x=3
z=f(x)
print('x=',x)
print('z=',z)
z()

Output

x= 4
z= 4
x= abc
x= 4
x= 3
z= <function f.<locals>.g at 0x000000F6919EF9D8>
x= abc

I don't understand how we call z() as a function when it is a variable. Also, I don't understand how we got the last 2 lines of output.

f(x) returns g which is a function, hence calling z() will call g(). — Austin
– Austin, Commented Aug 11, 2019 at 6:21
@Austin but z=f(x), so why does calling z() not execute the print statements in f()? — user456
– user456, Commented Aug 11, 2019 at 6:34
@Austin the statement z=f(x) executes all the print statements within f, then why is z() different? — user456
– user456, Commented Aug 11, 2019 at 6:42
please read the answer posted below. z is holding only the returned value from function f(x). That returned value happened to be a function. So calling z() calls that function and that function includes only one print statement. — Austin
– Austin, Commented Aug 11, 2019 at 6:44

hiro protagonist · Accepted Answer · 2019-08-11 06:22:34Z

7

in python all objects are first class objects. you can assign names (variables) to any object; that includes functions.

the relevant parts of your first question are:

def f(x):
    def g():
        x='abc'
    return g

i.e. f returns a function. you can assign and call it with:

z = f(3)
print(z)  # <function f.<locals>.g at 0x000000F6919EF9D8>
z()

for your second question: print(z) (see in the code above) will generate a line of output and calling z() (i.e. g()) will print x= abc.

answered Aug 11, 2019 at 6:22

hiro protagonist

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