Python me Functions kya hote hain?

Function ek reusable block of code hai jo ek specific kaam karta hai. Ek baar function define karo, aur jab chahein baar baar call karo — code dobara likhne ki zarurat nahi. Jaise ek machine jo ek specific kaam karna jaanti hai — button dabao aur kaam ho jaata hai.

Functions kyun use karte hain :-

Reusability — ek baar likho, baar baar use karo
Readability — code clean aur samajhne mein aasaan hota hai
Modularity — bade program ko chhote parts me todna
Less Errors — ek jagah change karo, sabko faayda

Is page me yeh sab sikhenge :-

1. Function define aur call karna
2. Parameters aur Arguments
3. Default Parameters
4. Keyword Arguments
5. *args aur **kwargs
6. return Statement
7. Multiple Return Values
8. Variable Scope — Local aur Global

1. Function Define aur Call Karna

Python me function def keyword se define hota hai. Function ka naam likhne ke baad parentheses () aur colon (:) lagate hain. Function ka body indented hoti hai.

Syntax
def function_name(): # function ka kaam # yahan code likhte hain function_name() # function call karna

Example 1: Simple function — bina parameters ke

Python

In [1]:

def greet():
    print("Namaste! Python me aapka swagat hai.")
    print("Aaj ka din accha ho!")

# Function call karo
greet()
greet()   # baar baar call kar sakte hain
greet()

Output

Example 2: Function se code reuse karna

Python

In [1]:

def print_line():
    print("-" * 40)

def show_menu():
    print_line()
    print("1. Naya Game")
    print("2. Load Game")
    print("3. Settings")
    print("4. Exit")
    print_line()

show_menu()

Output

2. Parameters aur Arguments

Parameter woh variable hai jo function define karte waqt likhte hain. Argument woh actual value hai jo function call karte waqt dete hain.

Example 1: Ek parameter wala function

Python

In [1]:

def greet_user(name):      # name = parameter
    print(f"Namaste, {name}!")

greet_user("Rahul")        # "Rahul" = argument
greet_user("Priya")
greet_user("Arjun")

Output

Example 2: Multiple parameters

Python

In [1]:

def add(a, b):
    result = a + b
    print(f"{a} + {b} = {result}")

def student_info(name, age, city):
    print(f"Name: {name}, Age: {age}, City: {city}")

add(10, 20)
add(55, 45)
student_info("Neha", 21, "Mumbai")

Output

3. Default Parameters

Kisi parameter ki default value set kar sakte hain. Agar function call karte waqt woh argument nahi diya jaata, toh default value use hoti hai.

Example 1: Default parameter ke saath function

Python

In [1]:

def greet(name, msg="Aapka din accha ho!"):
    print(f"Namaste {name}! {msg}")

greet("Rahul")                        # default msg use hoga
greet("Priya", "Happy Birthday!")     # custom msg diya
greet("Arjun", "All the best!")

Output

Example 2: Power function — default exponent 2

Python

In [1]:

def power(base, exp=2):
    return base ** exp

print(power(5))        # 5^2 = 25   (default exp=2)
print(power(3))        # 3^2 = 9
print(power(2, 10))    # 2^10 = 1024
print(power(7, 3))     # 7^3 = 343

Output

4. Keyword Arguments

Normally arguments order ke hisaab se dene padte hain. Lekin keyword arguments me aap parameter ka naam likhke argument de sakte hain — order matter nahi karta.

Example 1: Keyword arguments — order matter nahi karta

Python

In [1]:

def order_pizza(size, crust, topping):
    print(f"Pizza: {size} size, {crust} crust, {topping} topping")

# Positional — order matter karta hai
order_pizza("Large", "Thin", "Paneer")

# Keyword — kisi bhi order me de sakte hain
order_pizza(topping="Mushroom", size="Medium", crust="Thick")
order_pizza(crust="Stuffed", topping="Corn", size="Small")

Output

5. *args aur **kwargs

Jab pata nahi kitne arguments milenge, tab *args aur **kwargs use karte hain.

Type	Syntax	Kaam	Data milta hai
*args	def f(*args)	Multiple positional arguments	Tuple me
**kwargs	def f(**kwargs)	Multiple keyword arguments	Dictionary me

Example 1: *args — kitne bhi positional arguments

Python

In [1]:

def total(*args):
    print("Arguments:", args)   # tuple milta hai
    return sum(args)

print(total(10, 20))
print(total(5, 10, 15, 20))
print(total(1, 2, 3, 4, 5, 6, 7, 8, 9, 10))

Output

Example 2: **kwargs — kitne bhi keyword arguments

Python

In [1]:

def show_profile(**kwargs):
    print("--- Profile ---")
    for key, value in kwargs.items():
        print(f"  {key}: {value}")

show_profile(name="Rahul", age=22, city="Delhi")
print()
show_profile(name="Priya", age=21, city="Mumbai", job="Engineer", hobby="Painting")

Output

Example 3: *args aur **kwargs dono saath

Python

In [1]:

def my_function(name, *hobbies, **details):
    print(f"Name: {name}")
    print("Hobbies:", hobbies)
    print("Details:", details)

my_function("Arjun",
            "Cricket", "Coding", "Reading",
            age=23, city="Pune", job="Developer")

Output

6. return Statement

return se function ek value wapas bhejta hai — jise hum variable me store kar sakte hain ya seedha use kar sakte hain. return milte hi function band ho jaata hai.

Example 1: return se value wapas lena

Python

In [1]:

def square(n):
    return n ** 2

def is_even(n):
    return n % 2 == 0

# Return value variable me store karo
result = square(7)
print("7 ka square:", result)

# Ya seedha use karo
print("25 ka square:", square(25))
print("10 even hai?:", is_even(10))
print("7 even hai? :", is_even(7))

Output

Example 2: return se function jaldi band ho jaata hai

Python

In [1]:

def divide(a, b):
    if b == 0:
        return "Error: Zero se divide nahi kar sakte!"
    return a / b   # yeh sirf tab chalega jab b != 0

print(divide(10, 2))
print(divide(15, 3))
print(divide(5, 0))   # early return se error handle ho gaya

Output

7. Multiple Return Values

Python me function ek se zyada values return kar sakta hai — values tuple me wapas aati hain aur inhe unpacking se alag variables me le sakte hain.

Example 1: Do values return karna

Python

In [1]:

def min_max(numbers):
    return min(numbers), max(numbers)   # tuple return hota hai

nums = [34, 12, 78, 5, 90, 23, 67]

# Ek sath dono values lo
result = min_max(nums)
print("Tuple:", result)

# Ya unpack karo
smallest, largest = min_max(nums)
print("Minimum:", smallest)
print("Maximum:", largest)

Output

Example 2: Student result — multiple values return karna

Python

In [1]:

def analyze_marks(marks_list):
    total   = sum(marks_list)
    average = total / len(marks_list)
    highest = max(marks_list)
    lowest  = min(marks_list)
    grade   = "A" if average >= 85 else "B" if average >= 70 else "C"
    return total, average, highest, lowest, grade

marks = [88, 92, 76, 85, 90]
total, avg, high, low, grade = analyze_marks(marks)

print(f"Total  : {total}")
print(f"Average: {avg:.1f}")
print(f"Highest: {high}")
print(f"Lowest : {low}")
print(f"Grade  : {grade}")

Output

8. Variable Scope — Local aur Global

Local variable — function ke andar banaya, sirf wahan accessible.
Global variable — function ke bahar banaya, poore program me accessible.

Example 1: Local vs Global scope

Python

In [1]:

city = "Delhi"   # Global variable

def show_city():
    country = "India"   # Local variable — sirf yahan accessible
    print("City   :", city)     # global variable access ho sakta hai
    print("Country:", country)

show_city()
print("City (outside):", city)

# Local variable bahar access nahi hoga
try:
    print(country)
except NameError as e:
    print("Error:", e)

Output

Example 2: global keyword — function ke andar global variable change karna

Python

In [1]:

count = 0   # global variable

def increment():
    global count   # global keyword se global variable access
    count += 1
    print("Count inside function:", count)

increment()
increment()
increment()
print("Count outside:", count)

Output

Quick Summary — Functions ek nazar me

Concept	Kaam	Example
def	Function define karo	def greet():
Call	Function chalao	greet()
Parameters	Input variables	def f(a, b):
Arguments	Actual values	f(10, 20)
Default param	Fallback value	def f(n=5):
Keyword args	Name se argument do	f(b=2, a=1)
*args	Multiple positional	def f(*args):
**kwargs	Multiple keyword	def f(**kwargs):
return	Value wapas bhejo	return result
Multiple return	Kai values return	return a, b, c
Local scope	Function ke andar	sirf function me
Global scope	Poore program me	global x

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