Python call function from another function

You can call many functions from another function in Python. Each of the functions we write can be used and called from other functions we write.

# function definition
def fun():
    print("Called fun()")


# calling a function
fun()

You can do something like this:

def addOne(x):
    return x+1

def useFunction(addOne, x):
    return addOne(x)**2

Python call function from another function

Simple example code.

def fun2():
    print("Called by fun1()")


def fun1():
    print("Called by main function")
    fun2()  # calling fun2() from fun1()


fun1()

Output:

Use a function Output as an Input of another function

# Method 1: using return value inside another function

def fun1(a):
    res = a + 1
    return res


def fun2(c):
    res = c * 2
    return res


output = fun1(fun2(1))
print(output)


# Method 2: directly calling one function in the other
def function_1(n):
    v = n * n
    num = function_2(v)
    return num


def function_2(a_number):
    a_number = a_number * 2
    return a_number


print(function_1(10))

Output:

3
200

Call a nested function (function inside another function)

Create a nested function attribute like so:

def foo():
    # for closures or strictly local function
    # then this is useful!
    # ugly hack other wise to try and create methods.
    def bar():
        print('bar')    
    
    # if there are multiple function, return a container...
    return bar

Then:

foo.bar=foo()
foo.bar()
# prints 'bar'

But, this is far easier with a class:

class Foo:
    # class can hold related methods, setters and getters, 
    # protected variables, etc. 
    # Python is DESIGNED to do this.
    def bar(self):
        print('bar')

Then:

f=Foo()
f.bar()
# prints 'bar'

Do comment if you have any doubts or suggestions on this Python function topic.

Note: IDE: PyCharm 2021.3.3 (Community Edition)

Windows 10

Python 3.10.1

All Python Examples are in Python 3, so Maybe its different from python 2 or upgraded versions.