Understanding Python Functions: Definition, Scope, and Calls

Functions improve an application's modularity and code reuse; Python provides many built‑in functions such as print() and also allows developers to define their own functions.

Definition : A function is declared using the def keyword followed by the function name and an optional parameter list in parentheses. The typical structure is:

def function_name(parameter_list): """docstring (optional)""" # function body return [expression] # optional

Scope : Variables created inside a function have local scope, while variables defined outside have global scope. A function can read a global variable but cannot assign to it unless the global statement is used. Example:

a = 5 # global variable def func1(): print('func1() print a =', a) def func2(): a = 21 # local variable print('func2() print a =', a) def func3(): global a a = 10 # modifies global a print('func3() print a =', a) func1() func2() func3() print('the global a =', a)

Function Calls :

1. Positional arguments – arguments are passed in the order defined. Example:

def fun(name, age, gender): print('Name:', name, 'Age:', age, 'Gender:', gender, end='') fun('Jack', 20, 'man')

2. Keyword arguments – arguments are passed as keyword=value , allowing any order. Example:

def fun(name, age, gender): print('Name:', name, 'Age:', age, 'Gender:', gender, end='') fun(gender='man', name='Jack', age=20)

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