Python 101: Ultimate Python Guide or Introduction to Modern Python

Introduction

Python is a dynamically typed language, i.e., the data type of any variable or function is checked at run time, and due to this, python does not require the definition of data type as in java(Although you can define your data type in python which is not a must). Python is applied in fields such as web development, game development, AI and Machine learning, software development, etc. The article discusses python's basics and how to get started with the python programming language.

Variable Declaration

Variables are containers for storing values of the data.
Example of how to declare and assign values to variable

name = "John"
age = 45

As seen above there is no data type for each variable but data type for each variable can be done as shown

age = int(56) #age will be intenger
height = str(10) #height will be string

or

age:int = 56 #age will be intenger
height:str = 10 #height will be string

Data type that a function return can be specified as shown

def hello() ->int:
return 6

NB Declaration of datatype is not mostly done

Comments

Comment are not executed and they are for code explanation

Single Line Comments

# put comment here

Multi-line Comments

"""
This is a multline
comment
"""

Data Types

These include int, str, boolean and we have already seen how you can specifies them if you want

Data Structures(Collections/Arrays) in Python

These are dictionaries, list, tuples, and sets.

Lists

• Elements are ordered, changeable and allow duplicates
• Items can be added or removed
• Defined using [] or the list() constructor
• Use dot(.) to get in-build method to perform sort, remove etc

numbers = [10,23,90] #declaring using []
num =list((1, 4, 6)) #list constructor, note the double brackets

Sets

• Unordered, unchangeable, unindexed, and do not allow duplicate values
• Items in a set cannot be accessed using index but can be accessed using loop

num_set = {1, 3, 6, 70}
print(num_set )

a) Sets Union (|)

This combination of everything in the sets

lettersA = {"A", "B", "C", "D"}
lettersB = {"E", "F"}
print(lettersA | lettersB )

Results:

{'A', 'D', 'C', 'E', 'B', 'F'}

b) Sets Intersection(&)

This what is common between the given sets

lettersA = {"A", "B", "C", "D"}
lettersB = {"B", "G"}
print(lettersA & lettersB )

Results:

{'B'}

c) Sets Difference(-)

Deference A-B means what is in A and not in B

lettersA = {"A", "B", "C", "D"}
lettersB = {"B", "E", "F"}
print(lettersA - lettersB )

Results:

{'C', 'A', 'D'}

Dictionaries

They are unordered mutable python container that stores mappings of the unique keys to values

• They are ordered , changeable, and do not allow dublicates(from python 3.7 and above)

student = {
    "name" : "john",
    "age" : 34,
    "address" : "US"
}

print(student["name"])

Results:

john

Tuples

• Items are ordered, unchangeable, and allow duplicates values
• Items can be accessed by referring to the index number, inside square brackets

names= ("apple", "banana", "cherry")
print(names)

results

('apple', 'banana', 'cherry')

Conditional Statements

If Statement

Executes is the given condition is true

a = 4
b = 10
if b > a:
   print("B is greater than A")

Results:

B is greater than A

If ELse Statement

if executes when given condition is true and else executes when the condition fails

b = 4
a = 10
if b > a:
   print("B is greater than A")
else:
   print("B is not greater than A")

Results:

B is not greater than A

if---elif--else

used to express multiple conditions

num = 0

if num > 0:
  print("Number Positive")
elif num == 0:
  print("Number is equal to 0")
else:
  print("Number is negative ")

Results:

Number is equal to 0

Loops

These are the while and for loops and they execute as long as the given condition is true

The while loop

The following executes as long as i is < 5

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

Results:

1
2
3
4

For loop

A for loop is used for iterating over a sequence (that is either a list, a tuple, a dictionary, a set, or a string).
The following will print each fruits

fruits = ["apple", "banana", "mango"]
for x in fruits:
  print(x)

apple
banana
mango

Functions and Function Call

Function is a block of code that will executes when it is called

def helloWorld():
  print("Hello code Gurus")

helloWorld()# function Call

Results

Hello code Gurus

Passing Parameters and Arguments to Functions

• Parameters are variables in method while arguments are data passed to the method's parameters
• Arguments is the actual value of the variable that get passed to function

def helloWorld(name):
  name = 'Hello code Gurus'
  print(name)

helloWorld(name)

Results:

Hello code Gurus