unit-02

Statements and Control Structures in Python

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1. Assignment Statement

Definition: Assigns a value to a variable.

Syntax:

variable_name = value

Example:

x = 10
name = "Alice"
pi = 3.1416

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2. Import Statement

Definition: Used to include external modules or libraries in the program for additional functionalities.

Syntax:

import module_name

Example:

import math
print(math.sqrt(16))  # Output: 4.0

Import specific functions:

from math import sqrt
print(sqrt(25))  # Output: 5.0

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3. Print Statement

Definition: Outputs information or variables to the console.

Syntax:

print(value1, value2, ..., sep='separator', end='end')

Examples:

print("Hello, World!")
print("Python", "is", "fun", sep="-")  # Output: Python-is-fun
print("Hi", end="!")                    # Output: Hi!
print(10, 20, 30)

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4. if: elif: else: Statement

Definition: Used for decision making; executes code based on conditions.

Syntax:

if condition1:
    # block 1
elif condition2:
    # block 2
else:
    # block 3

Example:

score = 85
if score >= 90:
    print("Grade A")
elif score >= 80:
    print("Grade B")
else:
    print("Grade C")

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5. for Statement and while Statement

for Loop: Repeatedly executes a block for each item in a sequence.

Syntax:

for variable in iterable:
    # block

Example:

for i in range(5):
    print(i)  # Outputs 0 to 4

while Loop: Repeats as long as a condition is true.

Syntax:

while condition:
    # block

Example:

count = 0
while count < 5:
    print(count)
    count += 1

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6. continue and break Statements

continue: Skips the current iteration and moves to the next loop iteration.

Example:

for i in range(5):
    if i == 2:
        continue
    print(i)
# Output: 0 1 3 4

break: Stops the loop entirely when called.

Example:

for i in range(5):
    if i == 3:
        break
    print(i)
# Output: 0 1 2

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7. try: except Statement

Definition: Used for exception handling; code in try block runs, exceptions caught in except.

Syntax:

try:
    # code that might cause exception
except ExceptionType:
    # code to handle exception

Example:

try:
    x = 10 / 0
except ZeroDivisionError:
    print("Cannot divide by zero")

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8. raise Statement and with Statement

raise: Manually triggers an exception.

Syntax:

raise ExceptionType("Error message")

Example:

def check_age(age):
    if age < 0:
        raise ValueError("Age cannot be negative")

with: Simplifies exception handling with resources (like files), ensuring cleanup.

Syntax:

with open("file.txt", "r") as file:
    content = file.read()

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9. del and case Statement

del: Deletes variables, list items, dictionary entries, or object attributes.

Syntax:

del variable
del list[index]
del dict[key]

Example:

x = 10
del x
my_list = [1, 2, 3]
del my_list[^1]

case Statement: Python doesn’t have a built-in case statement like some languages, but Python 3.10+ has match-case for pattern matching.

Syntax:

match variable:
    case pattern1:
        # block
    case pattern2:
        # block
    case _:
        # default block

Example:

def number_to_string(num):
    match num:
        case 1:
            return "One"
        case 2:
            return "Two"
        case _:
            return "Other"
 
print(number_to_string(2))  # Output: Two

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This completes the detailed, syntax-rich notes for the “Statements and Control Structures” unit with definitions, usage, and examples.

Say “next” to continue to the next unit: list/tuple/range. ^12345678

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Footnotes

1. https://www.codingal.com/coding-for-kids/blog/control-structures-in-python/ ↩

2. https://realpython.com/python-control-flow/ ↩

3. https://unstop.com/blog/control-statement-in-python ↩

4. https://www.geeksforgeeks.org/dsa/loops-and-control-statements-continue-break-and-pass-in-python/ ↩

5. https://www.pickl.ai/blog/control-statements-in-python/ ↩

6. https://www.kdnuggets.com/python-basics-syntax-data-types-and-control-structures ↩

7. https://docs.python.org/3/tutorial/controlflow.html ↩

8. https://www.geeksforgeeks.org/python/conditional-statements-in-python/ ↩