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Complex, Boolean, String, Type Casting & Immutability in Python

Complex Data Type (complex)

What is a Complex Number?

A complex number is represented as:

a + bj

Where:

  • a → real part
  • b → imaginary part
  • j → imaginary unit
    (j² = -1, so j = √-1)

⚠️ Python uses j, not i

Valid Complex Numbers

a = 5 + 2j
print(a)

a = 5 + 2J
print(a)

✅ Capital J is allowed ❌ i or I is not allowed

a = 5 + 2i   # ❌ Invalid

Checking Type

a = 5 + 2j
print(type(a))   # <class 'complex'>

Real Part with Different Number Systems

a = 0b1101 + 2j
print(a)   # (13+2j)

❌ Imaginary part must be decimal

a = 0b1101 + 0b101j   # ❌ Error

Operations on Complex Numbers

a = 2 + 2j
b = 5 + 3j

print(a + b)
print(a - b)
print(a * b)
print(a / b)

Access Real and Imaginary Parts

a = 2 + 2j

print(a.real)   # 2.0
print(a.imag)   # 2.0

Magnitude of Complex Number

a = 3 + 4j
print(abs(a))   # 5.0

Boolean Data Type (bool)

Boolean values can be only:

  • True
  • False

⚠️ Must start with capital T / F

Examples

a = True
print(type(a))   # bool

b = False
print(type(b))   # bool

❌ Invalid

a = false   # ❌ Error

Boolean from Comparison

a = 10
b = 20

c = a > b
print(c)         # False
print(type(c))   # bool

Boolean Arithmetic

Internally:

  • True → 1
  • False → 0
a = True
b = False

print(a + b)     # 1
print(a * b)     # 0
print(type(a + b))   # int

String Data Type (str)

What is a String?

Anything enclosed in quotes is a string.

' '    single quotes
" "    double quotes
''' ''' triple single quotes
""" """ triple double quotes (docstring)

❌ Python has no char type Single character is also a string

Examples

a = "Apple"
b = "A"
c = 'A'

All are str.

Quotes Inside Strings

a = 'Learning "python" is fun'
b = "Learning 'python' is fun"

Triple Quotes (Multi-line Strings)

a = """Learning
python
is
fun"""
print(a)

Works with ''' also.

String Indexing & Slicing

Indexing

-10 -9 -8 -7 -6 -5 -4 -3 -2 -1
 a  b  c  d  e  f  g  h  i  j
 0  1  2  3  4  5  6  7  8  9

a = "abcdefghij"
print(a[2])     # c
print(a[-8])    # c

Slicing Syntax

a[start : end : step]

Examples

a = "Learning python is fun"

print(a[9])          # p
print(a[9:15])       # python
print(a[:15])        # Learning python
print(a[:])          # full string

String Arithmetic

a = "Learning python is "
b = "fun"

print(a + b)
print(3 * b)

CLI Example

print("#" * 50)
print("Hello")
print("#" * 50)

String Length

a = "apple"
print(len(a))

Capitalize First Letter

a = "hello"
temp = a[0].upper() + a[1:]
print(temp)

Capitalize Last Letter

a = "hello"
temp = a[:-1] + a[-1].upper()
print(temp)

Type Casting in Python

Fundamental Data Types

  • int
  • float
  • complex
  • bool
  • str

int()

print(int(15.2))      # 15
print(int("123"))     # 123

❌ Invalid

int("10.5")
int("0b101")
int(2+4j)

float()

print(float(10))      # 10.0
print(float(True))    # 1.0

❌ Invalid

float(10+2j)
float("hello")

complex()

print(complex(10))
print(complex(10.5))
print(complex(True))
print(complex(False))
print(complex("10.5j"))
print(complex(10, 5))

bool()

print(bool(0))        # False
print(bool(10))       # True
print(bool(""))       # False
print(bool("False"))  # True

str()

print(str(10))
print(str(10.5))
print(str(3+6j))
print(str(True))

Immutability of Fundamental Data Types

What is Immutability?

Once an object is created, it cannot be changed. Any modification creates a new object.

Example

b = 10
print(id(b))

b = b + 3
print(id(b))

Another Example

a = 10
b = 10

print(id(a))
print(id(b))
print(a is b)   # True

Next: Immutability vs Mutability in Python