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Type Casting and Conversion

Type Casting and Conversion

Section titled “Type Casting and Conversion”

Introduction

Section titled “Introduction”

Type conversion is the process of converting a value from one data type to another. Python supports both implicit (automatic) and explicit (manual) conversion.

Implicit Conversion

Section titled “Implicit Conversion”

Python automatically converts types when it makes sense:

x = 5        # int
y = 2.0      # float
result = x + y  # Python converts x to float
print(result)    # 7.0 (float)


# bool + int
print(True + 5)   # 6 (True is treated as 1)

Explicit Conversion

Section titled “Explicit Conversion”

To Integer int()

Section titled “To Integer int()”
int("42")         # 42
int(3.9)          # 3 (truncates!)
int(True)         # 1
int("0xFF", 16)   # 255 (hex to int)

To Float float()

Section titled “To Float float()”
float("3.14")     # 3.14
float(42)         # 42.0
float("inf")      # inf

To String str()

Section titled “To String str()”
str(42)           # '42'
str(3.14)         # '3.14'
str([1,2,3])      # '[1, 2, 3]'

To Boolean bool()

Section titled “To Boolean bool()”
bool(0)           # False
bool(1)           # True
bool("")          # False (empty string)
bool("hello")     # True
bool([])          # False (empty list)
bool(None)        # False

To List/Tuple/Set

Section titled “To List/Tuple/Set”
list("hello")     # ['h', 'e', 'l', 'l', 'o']
tuple([1,2,3])    # (1, 2, 3)
set([1,1,2,3,3])  # {1, 2, 3} — removes duplicates

Common Errors

Section titled “Common Errors”
int("hello")     # ValueError: invalid literal
int("3.14")      # ValueError: can't convert float string directly
# Fix:
int(float("3.14"))  # First convert to float, then int → 3

Why It Matters

Section titled “Why It Matters”

Type casting is essential when handling user input (input() returns str), processing data from files/APIs, and ensuring correct arithmetic.

Interview Questions

Section titled “Interview Questions”

Q1: What is the difference between implicit and explicit type conversion?

A: Implicit conversion is automatic (e.g., int + float → float). Explicit requires a casting function like int(), float(), str().

Q2: What values are considered falsy in Python?

A: False, None, 0, 0.0, "", [], (), {}, set() — all evaluate to False in boolean context.

Practice Exercises

Section titled “Practice Exercises”
  1. Convert a float string “3.14” to an integer.
  2. Check all falsy values using bool().
  3. Parse user input and perform arithmetic with type conversion.