Module I — Fundamentals of Python

Unit 1

Features, Identifiers & Keywords

Python is an interpreted, high-level, dynamically typed, object-oriented language created by Guido van Rossum (1991). Key features: simple syntax, portable, extensible, free/open-source, large standard library.

Identifier Rules

Rule	Valid	Invalid
Letters, digits, underscore only	`my_var, x1`	`my-var, x@1`
Cannot start with digit	`_count, name`	`1count, 2name`
Case sensitive	`Age ≠ age`	—
Cannot be keyword	`myif`	`if, for, while`

Python Keywords (35)

FalseNoneTrueandasassertasyncawaitbreakclasscontinuedefdelelifelseexceptfinallyforfromglobalifimportinislambdanotorpassraisereturntrywhilewithyield

Unit 1

Variables, Data Types & Type Conversions

Type	Example	Notes
`int`	`x = 10`	Unlimited precision integers
`float`	`x = 3.14`	64-bit IEEE 754
`complex`	`x = 3+4j`	Real + imaginary part
`str`	`x = "hello"`	Immutable sequence of chars
`bool`	`x = True`	Subclass of int; True=1, False=0
`list`	`x = [1,2,3]`	Mutable ordered sequence
`tuple`	`x = (1,2,3)`	Immutable ordered sequence
`dict`	`x = {'a':1}`	Key-value pairs
`set`	`x = {1,2,3}`	Unordered, no duplicates

Type Conversion Functions

int("42")      # → 42
float(10)      # → 10.0
str(3.14)      # → "3.14"
bool(0)        # → False  (0, "", [], None → False; everything else → True)
list("abc")    # → ['a', 'b', 'c']
tuple([1,2])  # → (1, 2)

Unit 1–2

Operators, Precedence & Associativity

Category	Operators	Example
Arithmetic	`+ - * / // % **`	`17//3=5, 17%3=2, 2**3=8`
Comparison	`== != < > <= >=`	`5 != 3 → True`
Logical	`and or not`	`True and False → False`
Assignment	`= += -= *= /= //= %=`	`x += 5`
Bitwise	`& \| ^ ~ << >>`	`5 & 3 = 1`
Identity	`is, is not`	`x is None`
Membership	`in, not in`	`3 in [1,2,3]`

Precedence (high→low): ** → ~ + - (unary) → * / // % → + - → << >> → & → ^ → | → comparison → not → and → or
Associativity: Left-to-right except ** (right-to-left)

Unit 3

Input, Output, Import & Math Functions

# input() always returns string
name = input("Enter name: ")
age  = int(input("Enter age: "))

# print() with sep and end
print("Hello", name, sep=", ", end="!\n")
print(f"Age: {age}")          # f-string (preferred)
print("%.2f" % 3.14159)     # → 3.14

# range(start, stop, step)
list(range(1, 10, 2))       # → [1, 3, 5, 7, 9]

math module

import math
math.sqrt(16)   # 4.0
math.ceil(4.2)  # 5
math.floor(4.9) # 4
math.pow(2,8)   # 256.0
math.log(100,10)# 2.0
math.factorial(5) # 120
math.pi          # 3.14159...
math.e           # 2.71828...

Unit 4

Decision-Making Structures

# if / elif / else
if x > 0:
    print("positive")
elif x == 0:
    print("zero")
else:
    print("negative")

# Ternary (conditional expression)
result = "even" if x % 2 == 0 else "odd"

# Nested if
if a > 0:
    if b > 0:
        print("both positive")

Python has no switch/case (pre-3.10). Use if/elif chains or a dict mapping. Python 3.10+ has match/case.

Unit 5

Looping Structures

# while loop
i = 1
while i <= 5:
    print(i)
    i += 1

# for loop with range
for i in range(1, 6):
    print(i)

# for loop over iterable
for ch in "hello":
    print(ch)

# else on loop — runs if loop NOT broken
for i in range(5):
    print(i)
else:
    print("done")

Nested loops: Time complexity multiplies. O(n²) for two nested loops each running n times.

Unit 6

Control Statements

Statement	Effect	Works In
`break`	Exit loop immediately	`for`, `while`
`continue`	Skip rest of current iteration	`for`, `while`
`pass`	Do nothing (placeholder)	Anywhere

# break — find first even
for i in range(10):
    if i % 2 == 0:
        print(i); break

# continue — skip odd
for i in range(5):
    if i % 2 != 0: continue
    print(i)          # 0 2 4

# pass — empty function body
def todo():
    pass

Quick Review

Flashcards — Module I

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