Python me Dictionaries kya hoti hain?

Dictionary Python ka ek key-value pair collection hai. Jaise ek real dictionary me word (key) hota hai aur uska meaning (value) — exactly waise hi Python dict me bhi kaam hota hai. Aap key ke zariye directly value access kar sakte hain — koi index dhundhne ki zarurat nahi.

Dictionary ki 5 main khasiyatein hain :-

Key-Value Pairs — har item ek key aur value ka joda hota hai
Ordered — Python 3.7+ me insertion order maintain hota hai
Mutable — items add, update ya remove ho sakte hain
Keys Unique — ek key sirf ek baar ho sakti hai
Keys Immutable — key string, number ya tuple ho sakti hai (list nahi)

Is page me yeh sab sikhenge :-

1. Dictionary banana aur access karna
2. Items add, update aur delete karna
3. Dictionary Methods — keys, values, items, get, pop, update
4. Dictionary ke saath loops
5. Nested Dictionary
6. Dictionary Comprehension

1. Dictionary Banana aur Access Karna

Dictionary ko curly brackets { } me key: value pairs likh ke banate hain. Keys aur values ko colon ( : ) se alag kiya jaata hai, aur pairs ko comma ( , ) se.

Example 1: Dictionary banana — basic

Python

In [1]:

student = {
    "name"  : "Rahul",
    "age"   : 21,
    "city"  : "Delhi",
    "marks" : 88.5
}

print(student)
print("Type  :", type(student))
print("Length:", len(student))   # kitne key-value pairs hain

Output

Example 2: Value access karna — key se

Python

In [1]:

car = {"brand": "Tata", "model": "Nexon", "year": 2023, "price": 1200000}

# Method 1: square brackets se
print(car["brand"])
print(car["price"])

# Method 2: get() se — zyada safe (KeyError nahi aata)
print(car.get("model"))
print(car.get("color"))          # key nahi hai — None return
print(car.get("color", "White")) # default value de sakte hain

Output

Example 3: KeyError — galat key pe kya hota hai

Python

In [1]:

person = {"name": "Priya", "age": 25}

# [] se galat key — KeyError aayega
try:
    print(person["salary"])
except KeyError as e:
    print("KeyError:", e)

# get() se galat key — safe, None milega
print(person.get("salary"))          # None
print(person.get("salary", 50000))   # default value

Output

2. Items Add, Update aur Delete Karna

Dictionary mutable hai — isme baad me bhi items add, update ya delete kiye ja sakte hain.

Example 1: Naya item add karna aur existing update karna

Python

In [1]:

profile = {"name": "Arjun", "age": 22}
print("Original:", profile)

# Naya key-value add karo
profile["city"] = "Mumbai"
profile["job"]  = "Developer"
print("After add:", profile)

# Existing value update karo
profile["age"] = 23
print("After update:", profile)

Output

Example 2: Items delete karna — del aur pop()

Python

In [1]:

info = {"name": "Neha", "age": 28, "city": "Pune", "phone": "9876543210"}
print("Original:", info)

# del — key delete karo
del info["phone"]
print("After del:", info)

# pop() — delete karo aur value return karo
removed_city = info.pop("city")
print("Removed city:", removed_city)
print("After pop:", info)

# popitem() — last inserted item remove karta hai
info.popitem()
print("After popitem:", info)

Output

Example 3: update() — ek saath multiple keys update karna

Python

In [1]:

employee = {"name": "Vikram", "salary": 40000, "dept": "IT"}
print("Before:", employee)

# update() — existing update karo aur naya add karo ek saath
employee.update({"salary": 55000, "dept": "Backend", "city": "Bangalore"})
print("After update:", employee)

Output

3. Dictionary Methods

Python dict ke saath bahut saare built-in methods aate hain jo kaam ko aasaan banate hain.

Example 1: keys(), values() aur items()

Python

In [1]:

marks = {"Maths": 92, "Science": 87, "English": 78, "Hindi": 95}

print("Keys  :", list(marks.keys()))    # sirf keys
print("Values:", list(marks.values()))  # sirf values
print("Items :", list(marks.items()))   # (key, value) tuples ki list

# Check karo key exist karti hai ya nahi
print("Maths in marks:", "Maths" in marks)
print("PE in marks   :", "PE" in marks)

Output

Example 2: setdefault(), copy() aur clear()

Python

In [1]:

config = {"theme": "dark", "font_size": 14}

# setdefault() — key na ho toh default value set karo
config.setdefault("language", "Hindi")   # nahi tha — add ho gaya
config.setdefault("theme", "light")      # tha — change NAHI hua
print("After setdefault:", config)

# copy() — independent copy banana
original = {"a": 1, "b": 2}
copy_d   = original.copy()
copy_d["c"] = 3
print("Original:", original)   # unchanged
print("Copy    :", copy_d)

Output

Example 3: fromkeys() — keys ki list se dict banana

Python

In [1]:

subjects = ["Maths", "Science", "English", "Hindi"]

# fromkeys() — saari keys ko same default value se initialize karo
scores = dict.fromkeys(subjects, 0)
print("Default scores:", scores)

# Ab individually update karo
scores["Maths"]   = 95
scores["Science"] = 88
print("Updated:", scores)

Output

4. Dictionary ke saath Loops

Dictionary pe for loop chalane ke 3 tarike hain — sirf keys, sirf values, ya dono saath items() se.

Example 1: Keys, Values aur Items pe loop

Python

In [1]:

prices = {"Apple": 80, "Mango": 60, "Banana": 20, "Grapes": 120}

print("--- Keys ---")
for fruit in prices:          # by default keys milti hain
    print(fruit)

print("\n--- Values ---")
for price in prices.values():
    print(price)

print("\n--- Key + Value ---")
for fruit, price in prices.items():
    print(f"{fruit}: Rs.{price}")

Output

Example 2: Loop se calculations — total marks aur average

Python

In [1]:

report = {"Maths": 92, "Science": 85, "English": 78, "Hindi": 90, "SST": 88}

total = 0
for subject, score in report.items():
    total += score
    grade = "A" if score >= 90 else "B" if score >= 80 else "C"
    print(f"{subject:10}: {score}  ({grade})")

avg = total / len(report)
print(f"\nTotal: {total}  |  Average: {avg:.1f}")

Output

5. Nested Dictionary

Dictionary ke andar doosri dictionary — isse Nested Dictionary kehte hain. Real applications me yeh bahut use hota hai — jaise user profiles, product catalog, JSON data, etc.

Example 1: Nested dict banana aur access karna

Python

In [1]:

students = {
    "s001": {"name": "Rahul",  "age": 20, "marks": 88},
    "s002": {"name": "Priya",  "age": 21, "marks": 95},
    "s003": {"name": "Arjun",  "age": 19, "marks": 76}
}

# Poori nested dict print karo
for roll, info in students.items():
    print(f"{roll}: {info}")

print()
# Ek specific student ka ek field access karo
print("s002 ka naam  :", students["s002"]["name"])
print("s001 ke marks :", students["s001"]["marks"])

Output

Example 2: Nested dict me update karna aur loop chalana

Python

In [1]:

company = {
    "emp001": {"name": "Rohit",  "dept": "IT",      "salary": 60000},
    "emp002": {"name": "Sunita", "dept": "HR",      "salary": 45000},
    "emp003": {"name": "Karan",  "dept": "Finance", "salary": 55000}
}

# Ek employee ka salary update karo
company["emp001"]["salary"] = 70000

# Saare employees ka naam aur salary print karo
print(f"{'Name':<10} {'Dept':<10} {'Salary':>10}")
print("-" * 32)
for emp_id, details in company.items():
    print(f"{details['name']:<10} {details['dept']:<10} {details['salary']:>10}")

Output

6. Dictionary Comprehension

List comprehension ki tarah Dictionary Comprehension se hum ek hi line me nai dictionary bana sakte hain — loop aur condition ke saath.

Syntax
{key: value for item in iterable if condition}

Example 1: Squares dictionary — number: uska square

Python

In [1]:

# Normal tarika
squares_normal = {}
for n in range(1, 6):
    squares_normal[n] = n ** 2
print("Normal    :", squares_normal)

# Dict Comprehension — ek line me!
squares_comp = {n: n**2 for n in range(1, 6)}
print("Comprehension:", squares_comp)

Output

Example 2: Condition ke saath — sirf passing marks wale

Python

In [1]:

all_marks = {"Rahul": 85, "Priya": 42, "Arjun": 91, "Neha": 38, "Vikram": 76}

# Sirf jo 50 se zyada marks hain
passed = {name: score for name, score in all_marks.items() if score >= 50}
print("Passed:", passed)

# Keys ko uppercase karo
upper_keys = {k.upper(): v for k, v in all_marks.items()}
print("Upper keys:", upper_keys)

Output

Example 3: Do lists se dictionary banana — zip() se

Python

In [1]:

names  = ["Laptop", "Phone", "Tablet", "Watch"]
prices = [55000, 18000, 25000, 8000]

# zip() se dono lists pair ho jaati hain
catalog = {item: price for item, price in zip(names, prices)}
print("Catalog:", catalog)

# Sirf 20000 se saste products
budget = {item: price for item, price in catalog.items() if price <= 20000}
print("Budget items:", budget)

Output

Quick Summary — Dictionary Methods ek nazar me

Method / Operation	Kaam	Example
d[key]	Value access — KeyError possible	d["name"]
get(key, default)	Safe value access	d.get("name", "N/A")
d[key] = val	Add ya update	d["age"] = 25
update()	Multiple add/update	d.update({"a":1})
del d[key]	Key delete karo	del d["name"]
pop(key)	Delete + return value	d.pop("age")
popitem()	Last item remove	d.popitem()
keys()	Saari keys	d.keys()
values()	Saari values	d.values()
items()	key-value tuples	d.items()
setdefault()	Key nahi ho toh default set	d.setdefault("x", 0)
copy()	Independent copy	d2 = d.copy()
clear()	Sab hatao	d.clear()
fromkeys()	Keys list se dict banana	dict.fromkeys(lst, 0)

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