Chapter 8 Strings . Chapter 9 Lists . Chapter 10 Tuples & Dictionary

  🔤 Strings

• Definition: Sequence of characters enclosed in quotes.
• Example: str1 = "Hello" → "Hello"

📋 Lists

• Definition: Ordered, mutable collection enclosed in square brackets.
• Example: list1 = [10, 20, 30] → [10, 20, 30]

🔗 Tuples

• Definition: Ordered, immutable collection enclosed in parentheses.
• Example: tuple1 = (1, 2, 3) → (1, 2, 3)

📖 Dictionaries

• Definition: Unordered collection of key–value pairs enclosed in curly braces.
• Example: dict1 = {'Math': 90, 'Sci': 85} → {'Math': 90, 'Sci': 85}

⚙️ Key Properties

• Strings: Indexed, immutable.
  Example → "python"[0] → 'p'

• Lists: Indexed, mutable.
  Example → list1[2] = 35 → [10, 20, 35]

• Tuples: Indexed, immutable (but can hold mutable objects).
  Example → (7, 8, [55, 66])[2][1] = 100 → (7, 8, [55, 100])

• Dictionaries: Keys unique, values mutable.
  Example → dict1['Math'] = 95 → {'Math': 95, 'Sci': 85}

➕ Operators

• Concatenation (+): "hi"+"bye" → "hibye"; [1]+[2] → [1,2]; (1,)+(2,) → (1,2)
• Repetition ():* "ha"*3 → "hahaha"; [3]*2 → [3,3]; (4,)*3 → (4,4,4)
• Membership (in / not in): "a" in "cat" → True; 10 in [2,4,6] → False

✂️ Slicing

• Strings: "computer"[1:5] → "ompu"
• Lists: [2,4,6,8,10][2:4] → [6,8]
• Tuples: (10,20,30,40)[1:3] → (20,30)

🔄Traversal

• For loop:

  for ch in "code": print(ch)
  # c o d e
  

• While loop:

  i=0; s="hi"
  while i<len(s): print(s[i]); i+=1
  # h i
  

🛠️ Common Methods

Strings

• len("hi") → 2
• "hello".upper() → "HELLO"
• "HELLO".lower() → "hello"
• "hello world".split() → ['hello','world']

Lists

• list1.append(5) → [10,20,5]
• list1.remove(20) → [10,5]
• list1.sort() → [5,10]

Tuples

• (10,20,10).count(10) → 2
• (10,20,30).index(20) → 1

Dictionaries

• dict1.keys() → ['Math','Sci']
• dict1.values() → [90,85]
• dict1.get('Math') → 90

NOTE

Strings , Lists , Tuples & Dictionary begins with Position Zero in forward direction

Strings , Lists , Tuples & Dictionary begins with Position -1 in Reverse  direction

Royale in Forward Reading
R is Position Zero

e is Position Five

Python in Reverse Reading
R is Position -6

e is Position -1

Comparison Table

 🎯 Mnemonic for Brackets

Think of the phrase:
“Quotes, Squares, Circles, Curly”

• Quotes → Strings
  "Hello" → Characters are always spoken in quotes

• Squares → Lists
  [1,2,3] → Lists are like boxes (square shelves) where items can be changed

• Circles → Tuples
  (1,2,3) → Tuples are round plates — once served, you can’t change the food

• Curly → Dictionaries
  {'key': 'value'} → Curly braces look like locks protecting key–value pairs

🧠 Quick Memory Trick

“Quotes talk, Squares store, Circles stay, Curly connect.”

• Quotes talk → Strings are words/characters.
• Squares store → Lists store items flexibly.
• Circles stay → Tuples stay fixed.
• Curly connect → Dictionaries connect keys to values.