Python Core Concepts

1. Variables

var1 = "hello"
item = "Code 101"
print(type(item))

2. Comments

# Example of a single-line comment

3. Numbers (int and float)

When comparing floats directly, we may run into precision issues:

0.1 * 3 == 0.3 # False

To tackle this, we can use the math.isclose() function:

import math

math.isclose(0.1 * 3, 0.3)  # True

4. Arithmetic Operations

• +, -, *, /
• / true division -> float
• // floor division -> integer or float
• % modulo -> remainder
• ** -> power

5. Strings

• Concatenation (+): Joins strings.
• Length (len()): Gets the number of characters.
• Indexing ([]): Access a character by position (0-based).
• Slicing ([:]): Extract substrings.
• .lower() / .upper(): Converts the entire string to uppercase or uppercase
• .strip() / .lstrip() / .rstrip(): Removes invisible whitespace and newline characters (\n) from the edges.
• .startswith() / .endswith(): Returns a Boolean (True or False) if the string starts/ends with a specific pattern.
• .split() : Breaks a string apart into a List, splitting it at a character you define.
• .join(): The exact reverse of split. Takes a List and glues it together into a single string.
• .replace(): Swaps a specific substring with another one.