April Python Bootcamp Day 7

 

Day 7: Strings in Python (Complete Guide)

Strings are one of the most powerful and frequently used data types in Python. From handling user input to building AI systems, strings are everywhere. Mastering them is non-negotiable if you want to become strong in programming.

---

 What is a String?

A string is a sequence of characters enclosed in quotes.

name = "Piyush"
city = 'Pune'
message = """Multi-line string"""

---

 String Indexing

Each character has a position (index).

text = "Python"

print(text[0])  # P
print(text[5])  # n

 Index starts from 0

---

 Negative Indexing

text = "Python"

print(text[-1])  # n
print(text[-2])  # o

 Access from the end

---

 String Slicing

Extract parts of a string.

text = "Python Programming"

print(text[0:6])   # Python
print(text[7:])    # Programming
print(text[:6])    # Python
print(text[::2])   # Pto rgamn

---

 String Immutability 

Strings cannot be changed after creation.

text = "hello"
# text[0] = "H" ❌ Error

✔ Correct approach:

text = "hello"
text = "H" + text[1:]

---

 Important String Methods 

 Case Conversion

text = "python"

print(text.upper())   # PYTHON
print(text.lower())   # python
print(text.title())   # Python

 Searching

text = "hello world"

print(text.find("world"))  # 6
print(text.count("l"))     # 3

 Replace

text = "I like Java"

print(text.replace("Java", "Python"))

 Strip Spaces

text = "  hello  "

print(text.strip())

 Split & Join

text = "apple,banana,mango"

fruits = text.split(",")
print(fruits)

print("-".join(fruits))

---

 String Concatenation

print("Hello" + " " + "World")

---

 String Formatting (Best Practice)

name = "Piyush"
age = 21

print(f"My name is {name} and I am {age} years old")

---

 Escape Characters

print("Hello\nWorld")
print("Hello\tWorld")
print("He said \"Python is awesome\"")

---

 Membership Operators

text = "Python"

print("Py" in text)        # True
print("Java" not in text)  # True

---

 Notes (Important)

• Strings are immutable
• Indexing starts from 0
• Strings are iterable
• Slicing is safe (no error if out of range)
• Prefer f-strings for formatting

Practice Questions

 Basic

• Print first and last character of a string
• Reverse a string using slicing
• Count total characters in a string
• Convert string to uppercase and lowercase

---

 Intermediate

• Check if a string is palindrome
• Count vowels and consonants
• Remove spaces from a string
• Find frequency of each character

---

 Advanced

• Check if two strings are anagrams
• Find the longest word in a sentence
• Implement your own replace() function
• Compress a string (e.g., "aaabb" → "a3b2")