Lameck Odhiambo

Posted on Sep 20

Python basics, Operators and Conditions

#beginners #python #tutorial

Introduction

Python is a high-level language (its closer to the natural language such as English compared to C++, Assembly which are low level languages - closer to the Machine language), general-purpose programming language known for its clear syntax and readability.

How python works

Python code in your source code is Compiled, the converted to Byte Code (which is a low level language) then to a Virtual Machine (which converts the code to 1s and 0s to be understood by the machine) after these steps the Output is produced.
The step from compiler to virtual machine is called Interpreter

Common Uses

Python is applied across many different industries and technical fields:

Web Development: Building server-side applications with frameworks like Django and FastAPI.
Data Science & Machine Learning: Processing numbers and training models using Pandas, NumPy, and PyTorch.
Automation: Writing simple scripts to handle repetitive daily file management or data entry tasks

Getting started with Python

Print()

Print() function displays values or text on the screen. It shows the result of a particular program that was run. Basically it displays an output of a program.

print("Hello World")

You can also use single quotes

print('Hello World')

A variable can also be printed as shown but in this case we do not use quatation

age = 30 print(age)

Variables

Variables are containers or box holding a particular value. It can be text, number or a float

first_name = 'Lameck' 
first_name = "Lameck"

print(first_name)

first_name here is a variable.

Data types in Python

Strings

Strings are surrounded by either single quatation marks or double quatation.

first_name = 'Lameck' 
first_name = "Lameck"

print(first_name)

'Lameck' here is a string

Integer

Integers are whole numbers and are not inside any quatatation.

age = 30
quantity = 3
number_of_students = 68

Float

Float are numbers containing a decimal point, also they are not put inside quatations.

price = 10.99
weight = 75.3

Booleans

These are True of False values. The are also not put inside the quatations and the first letters must be capital.

is_student = True
is_adult = False

Type Casting

Type casting is converting a variable to another data type. For example converting a float to an integer or a string to an integer and so forth.

gpa = 3.2
new_gpa = int(gpa)
print(new_gpa)

age = 32
new_age = float(age)
print(new_age)

F - Strings / String formatting

Format strings, f-strings or String formatting inserts variables, expressions, or specific formatting rules directly into a text string.

age = 33
name = "Nashon"
print(f"{name} is {age} years old.")

Input()

This is a function that prompts the user to enter data. It returns the entered value as a string.

name = input("Enter your name: ")
print(f"Hello {name}")

Operators in Python

1. Arithmetic operators

Used to perform standard mathematical calculations

2. Comparison (Relational) Operators

Used to compare two values. They always return a Boolean value: either True or False

3. Logical Operators

Used to combine conditional statements

and: Returns True if both statements are true

or: Returns True if at least one statement is true

not: Inverts the result (returns False if the result is true)

4. Membership Operators

Used to test if a sequence (like a string, list, or tuple) is present in an object.

in: Returns True if a sequence with the specified value is present in the object (e.g., 'a' in 'apple' → True).

not in: Returns True if a sequence with the specified value is not present in the object.

5. Identity Operators

Used to compare objects, not if they are equal, but if they are actually the same object with the same memory location.

is: Returns True if both variables point to the same object.

is not: Returns True if both variables do not point to the same object.

Conditions in Python

Conditional statements control the flow of execution by evaluating expressions to either True or False.
Operators discussed above can be used within these conditional statements.

1. The if Statement

Executes a block of code only if the condition evaluates to True

age = 20
if age >= 18:
    print("You are an adult.")  # Runs because the condition is True

2. The if-else Statement

Executes one block if the condition is True, and an alternate block if it is False

score = 45
if score >= 50:
    print("Passed")
else:
    print("Failed")

3. The if-elif-else Chain

Used to evaluate multiple sequential conditions. It stops evaluating as soon as it finds the first True condition

temperature = 25

if temperature > 30:
    print("It's hot.")
elif temperature >= 15:
    print("It's warm.")  # Runs and skips the rest
else:
    print("It's cold.")

Nested Conditions

Nested conditionals occur when you place a conditional statement (if, elif, or else) inside another conditional statement. They are used to test a secondary condition only after a primary condition has already passed.

is_logged_in = True
age = 20

if is_logged_in:
    print("User is authenticated.")

    # Secondary check inside the first one
    if age >= 21:
        print("Purchase approved.")
    else:
        print("Purchase denied: You must be at least 21.")

else:
    print("Purchase denied: Please log in first.")

Conclusion

Python operators and conditional statements are the fundamental building blocks that give programs the ability to process data, make decisions, and control execution flow.

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