Python 101:The Ultimate Beginner’s Guide

Python is a widely used high level general purpose programming language created by Guido van Rossum in 1991.

It is used for web development,software development,data analytics and Artificial Intelligence & Machine Learning.

Why Python

Python is widely preferred due to it's high capabilities below

• It has a simple syntax similar to English language hence simple to use and understand.
• Python runs on intepreter system meaning code can be executed as soon as it's written.You do not need to compile your program before executing it.
• Python supports 3 programming paradigms - its procedural,object-oriented and functional.
• Python has extensive library which includes almost every function imaginable

Python Basics

Variables in Python

A variable is a named location used to store data in memory and can hold different data types ie strings, integers, floats.
Python has no command for declaring a variable but rather created the moment it's assigned a value.

name = 'Maryam'
age = 62

Data Types

Variables can store data of different types, and different types can do different things. In Python, the data type is set when you assign a value to a variable.

Python has the following data types built-in by default:

Type	Example	Description
int	29	Whole numbers
float	1.25	Decimal numbers
str	"stylo"	Text data
bool	True, False	Boolean values
list	[40, 52, 13]	Ordered, mutable collection
tuple	(11, 23, 63)	Ordered, immutable collection
set	{1, 2, 3}	Unordered, unique values
dict	{"a": 1, "b": 2}	Key-value pairs

1.Strings

Strings in python are surrounded by either single quotation marks, or double quotation marks.
Assigning a string to a variable is done with the variable name followed by an equal sign and the string:

a = "Hello"
print(a)

# slicing strings.
name = 'Aubameyang'
print(name[3:7]) # returns characters from position 3 to position 7(not included)
# amey
print(name[:5]) # _returns characters from the start to position 5(not inclusive)_
#Aubam
print(name[2:]) # returns characters from position 2 all the way to the end.
#bameyang

Python has built in methods used to modify strings

a = "Hello, World!"
print(a.upper()) #returns string in upper case
# HELLO, WORLD!
print(a.lower()) # returns the string in lower case
# Concatenating strings
d = "Hello"
b = "World"
c = d + " " + b
print(c) # Hello World

2.Lists

A list is an ordered mutable collection that allows duplicate values.
List items can be of any data type
Lists are created using square brackets

thislist = ["apple", "banana", "cherry", "apple", "cherry"]
print(thislist)

# Identifying the data type

fruits = ["apple", "banana", "cherry"]
print(type(mylist)) # <class 'list'>

# Accessing items in  lists

mylist = ['apple', 'banana', 'cherry']
print(mylist[1]) # banana

#Changing list items

thislist = ["apple", "banana", "cherry"]
thislist[1] = "blackcurrant"
print(thislist) # ['apple', 'blackcurrant', 'cherry']

#Inserting an item at specified index

thislist = ["apple", "banana", "cherry"]
thislist.insert(2, "watermelon")
print(thislist) # ['apple', 'banana', 'watermelon', 'cherry']

# Adding an item at the end of the list

thislist = ["apple", "banana", "cherry"]
thislist.append("orange")
print(thislist) # ['apple', 'banana', 'cherry', 'orange']

# Removing specified item from the list

thislist = ["apple", "banana", "cherry"]
thislist.remove("banana")
print(thislist) # ['apple', 'cherry']

# Removing an item on specified index

thislist = ["apple", "banana", "cherry"]
thislist.pop(1)
print(thislist) # ['apple', 'cherry']

thislist = ["orange", "mango", "kiwi", "pineapple", "banana"]
thislist.sort()
print(thislist)

thislist = ["banana", "Orange", "Kiwi", "cherry"]
thislist.reverse()
print(thislist)

3.Tuples

A tuple is an ordered, immutable collection of items that allows duplicates.
Tuples are created using double brackets ()

# Creating a tuple
my_tuple = (1, 2, 3)



``# Tuple with mixed data types
person = ("Lenny", 25, True)``

# Accessing elements
print(person[0])  # Output: Lenny

# Slicing
print(my_tuple[1:])  # Output: (2, 3)

# Nested tuple
nested = (1, (2, 3), 4)

# Tuple with one item 
single = (5,)

4.Dictionary

A dictionary is an unordered, mutable collection of key-value pairs. It uses {} curly braces.

#Creating a dictionary

person = {
    "name": "Warner",
    "age": 25,
    "is_student": False
}
# Access value
print(person["name"])  # Output: Warner

# Modify value
person["age"] = 25

# Add new key-value pair
person["city"] = "Kisumu"

# Delete a key
del person["is_student"]

# A dictionary of people and their ages
people = {
    "Juliette": 28,
    "Kenji": 34,
    "Warner": 41
}


# Updating a value
people["Warner"] = 42

# Removing a person
people.pop("Juliette")

# Showing all keys and values
print("Keys(people.keys()) # dict_keys(['Kenji', 'Warner', 'Ella'])
print("Values:", people.values()) #dict_values([34, 42, 25])
print("Items:", people.items()) # dict_items([('Kenji', 34), ('Warner', 42), ('Ella', 25)])

Conditional Statements

Conditional statements in Python are used to execute certain blocks of code based on specific conditions. The conditional statement checks to see if a statement is True or False .

• The if statement

This is the simplest form of a conditional statement. It executes a block of code if the given condition is true.

age = 30

if age > 25:
    print("You're still a child")

This checks if the age is greater than 25. Since 30 > 25, the condition is True, so the message gets printed.

• If else statement

The if-else statement is used to execute both the true part and the false part of a given condition. If the condition is true, the if block code is executed and if the condition is false, the else block code is executed.

number = 51

if number % 2 == 0:
    print("The number is even.")
else:
    print("The number is odd.")

Since 51 is not divisible by two, the else statement is executed.

• Elif statement

elif statement in Python stands for "else if." It allows us to check multiple conditions , providing a way to execute different blocks of code based on which condition is true.

score = 73

if score >= 70:
    print("Grade: A")
elif score >= 60:
    print("Grade: B")
elif score >= 50:
    print("Grade: C")
else:
    print("Grade: D")

The statement checks each condition in order, and once it finds a condition that's true—like score >= 70 for a score of 73,it runs that block and skips the rest. Hence the output will be Grade :A

Conclusion

Understanding core concepts like variables, data types, and conditional statements is just the beginning.
Keep learning and experimenting ,Python’s capabilities are vast and the journey has just begun.