Basic Functions in Python

Basic functions flow:

• We define function in python using “def”
• Function can have n number of statements
• Function execute only when we call that function.
• Calling is a single statement used to access the function logic

def fun():
    print("Hello...")
    return

fun() # calling

• We cannot call a function before it has defined.
• Python is interpreted programming language, hence the code execute line by line from top to bottom.
• We cannot call the function before it is ready(not defined)

fun() # error : 

def fun():
    print("Hello...")
    return

• The main advantage of functions is code re-usability.
• We can call the function many times once we defined.

def test():
    print("logic..")
    return

test()
test()
test()

• One source file(.py file) can have more than one function definition.
• Functions get executed in the order we invoke.

def m1():
    print("m1.....")
    return

def m2():
    print("m2.....")
    return

m2()
m1()

We can access one function from another function.

def m1():
    print("control in m1...")
    return

def m2():
    print("control in m2...")
    m1() #calling
    print("control back to m2 from m1...")
    return

print("Program starts...")
m2() #calling
print("Program ends...")

Check the program execution:

print(1)

def test():
    print(3)
    return

print(2)
test()
print(4)

Output it:

print(7)

def m1():
    print(3)
    return

print(6)

def m2():
    print(2)
    return

print(9)
m2()
print(4)
m1()
print(0)

Output it:

def m1():
    print(2)
    return

print(7)
m1()
print(4)

def m2():
    print(2)
    m1()
    print(8)
    return

print(9)
m2()
print(6)