Course Content
Introduction to python
In this tutorial, you will learn the fundamentals of programming as well as the python programming language. You will also learn what makes python different from other programming languages. In addition you will learn some keywords in python as well as what comments are and datatypes in python. Furthermore, you will learn how to convert from one data type to another, input and output in python, operators and namespacing.
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Introduction and setting up your environment
Python Keywords and Identifiers
Python Statement, Indentation and Comments
Python variables
Python DataTypes
Python Conversion
Python Input/Output and Imports
Python Operators
Python Namespace
Python flow control
In this topic you will learn how computers typically run programs and how to structure your programs for optimum performance and output. You'll also learn how computers make decisions, and how they repeat things or do multiple things within a short time. Overall you'll learn the concept of getting a computer to do things based on a set of pre-written instructions.
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Python If…else Statement
Python For loop
Python While loop
Python Break and Continue
Python Break and Continue
Python pass statement
Python functions
The best programming practices include not doing the same thing all over again. Hence in this topic, you will learn to write programs that perform a specific thing and which you can reuse rather than write every time you need to. You will also learn how to create your own modules (which are python files) and export for use wherever they are needed.
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Python Functions
Python Function Arguments
Python Anonymous Functions
Python Global, Local and Nonlocal variables
Data Types
You will learn the fundamental data types needed to write efficient programs and also gain an intuitive understanding for which data type would be more efficient in different scenarios. You will learn the concept of lists, tuples, sets, strings, dictionaries...which are all fundamental data type that can be used to create sophisticated programs.
Python Files
In this topic, you will learn how to write scripts to manipulate files stored on your computer. And how to navigate your computer's directories to edit, delete and create new files using just python scripts. In addition, you will learn the concept of exception handling and how they can be used to make a program more efficient.
Python Objects and Classes
This topic sees us being introduced to Object-Oriented Programming (OOP) which is a programming style which follows the recommended guide of writing programs. In this topic, every thing in python is an object and you will learn how this is so. In addition you will learn how to write clean code for readability and better comprehension and which also follows PEP-8 (Python Enhancement Proposal) guidelines.
Python Advanced Topics
In this topic, you will learn about iterators, generators, closures, decorators and Regex in python. What this topic aims to achieve is to teach you advanced methods of writing python code to make your programs as concise as possible.
Python Date and Time
This topic aims to elevate your programming skills in python using the python date and time module. In this topic, you will be introduced to the concept of using the time module, and how to use this to measure the execution of your programs.
Python from zero to Hero
About Lesson

In this tutorial, you will learn about Python variables, constants, literals and the instances in which they are used.

PYTHON VARIABLES

A variable is a named location used to store data in the computer’s memory. It is helpful to think of variables as a container that holds data that can be changed later in the program. What this means can be illustrated with a simple analogy.
Consider a container for collecting specimen of live organisms, say cockroaches. What this simply means is that there will always be activities in the container due to the movement of the cockroaches. Consider filling a different container with sand. What do you think would happen? Answer this yourself.
For an example code,

number = 10

Here, we have created a variable named number. We have assigned the value 10 to the variable.

You can think of variables as a bag to store books in it and that book can be replaced at any time.

number = 10
number = 1.1

Initially, the value of number was 10. Later, it was changed to 1.1.

Note: In Python, we don’t actually assign values to the variables. Instead, Python gives the reference of the object(value) to the variable. This will be clear once we get to the part of Object-Oriented Programming.

Assigning values to Variables in Python

As you can see from the above example, you can use the assignment operator = to assign a value to a variable.

Example 1: Declaring and assigning value to a variable

website = "apple.com"
print(website)

Output

apple.com

In the above program, we assigned a value apple.com to the variable website. Then, we printed out the value assigned to website i.e. apple.com

Note: Python is a type-inferred language, so you don’t have to explicitly define the variable type. It automatically knows that apple.com is a string and declares the website variable as a string.

Example 2: Changing the value of a variable

Loading

In the above program, we have assigned apple.com to the website variable initially. Then, the value is changed to facebook.com.

Example 3: Assigning multiple values to multiple variables

a, b, c = 5, 3.2, "Hello"

print (a)
print (b)
print (c)

If we want to assign the same value to multiple variables at once, we can do this as:

x = y = z = "same"

print (x)
print (y)
print (z)

The second program assigns the same string to all the three variables x, y and z.

Now earlier I mentioned that things could be going on in a variable, and here’s an example:

a = 3 + 4

In this example, there’s a computation between 3 and 4 going on. And we can say there are activities going on the the variable ‘a’ above.

Constants

A constant is a type of variable whose value cannot be changed. It is helpful to think of constants as containers that hold information which cannot be changed later.

You can think of constants as a bag to store some books which cannot be replaced once placed inside the bag.

Assigning value to constant in Python

In Python, constants are usually declared and assigned in a module. Here, the module is a new file containing variables, functions, etc which is imported to the main file. Inside the module, constants are written in all capital letters and underscores separating the words.

Example 3: Declaring and assigning value to a constant

Create a constant.py:

PI = 3.14
GRAVITY = 9.8

Create a main.py:

import constant

print(constant.PI)
print(constant.GRAVITY)

Output

3.14
9.8

In the above program, we create a constant.py module file. Then, we assign the constant value to PI and GRAVITY. After that, we create a main.py file and import the constant module. Finally, we print the constant value.

Note: In reality, we don’t use constants in Python. Naming them in all capital letters is a convention to separate them from variables, however, it does not actually prevent reassignment.

Rules and Naming Convention for Variables and constants

  1. Constant and variable names should have a combination of letters in lowercase (a to z) or uppercase (A to Z) or digits (0 to 9) or an underscore (_). For example: 
    snake_case
MACRO_CASE
camelCase
CapWords
  2. Create a name that makes sense. For example, vowel makes more sense than v.
  3. If you want to create a variable name having two words, use underscore to separate them. For example: 
    my_name
current_salary
  4. Use capital letters possible to declare a constant. For example: 
    PI
G
MASS
SPEED_OF_LIGHT
TEMP
  5. Never use special symbols like !, @, #, $, %, etc.
  6. Don’t start a variable name with a digit.

Literals

Literal is a raw data given in a variable or constant. In Python, there are various types of literals they are as follows:

Numeric Literals

Numeric Literals are immutable (unchangeable). Numeric literals can belong to 3 different numerical types: Integer, Float, and Complex.

Example 4: How to use Numeric literals in Python?

a = 0b1010 #Binary Literals
b = 100 #Decimal Literal 
c = 0o310 #Octal Literal
d = 0x12c #Hexadecimal Literal

#Float Literal
float_1 = 10.5 
float_2 = 1.5e2

#Complex Literal 
x = 3.14j

print(a, b, c, d)
print(float_1, float_2)
print(x, x.imag, x.real)

Output

10 100 200 300
10.5 150.0
3.14j 3.14 0.0

In the above program,

  • We assigned integer literals into different variables. Here, a is binary literal, b is a decimal literal, c is an octal literal and d is a hexadecimal literal.
  • When we print the variables, all the literals are converted into decimal values.
  • 10.5 and 1.5e2 are floating-point literals. 1.5e2 is expressed with exponential and is equivalent to 1.5 * 102.
  • We assigned a complex literal i.e 3.14j in variable x. Then we use imaginary literal (x.imag) and real literal (x.real) to create imaginary and real parts of complex numbers.

String literals

A string literal is a sequence of characters surrounded by quotes. We can use both single, double, or triple quotes for a string. And, a character literal is a single character surrounded by single or double quotes.

Example 7: How to use string literals in Python?

strings = "This is Python"
char = "C"
multiline_str = """This is a multiline string with more than one line code."""
unicode = u"u00dcnicu00f6de"
raw_str = r"raw n string"

print(strings)
print(char)
print(multiline_str)
print(unicode)
print(raw_str)

Output

This is Python
C
This is a multiline string with more than one line code.
Ünicöde
raw n string

In the above program, This is Python is a string literal and C is a character literal.

The value in triple-quotes """ assigned to the multiline_str is a multi-line string literal.

The string u”u00dcnicu00f6de” is a Unicode literal which supports characters other than English. In this case, u00dc represents Ü and u00f6 represents ö.

r”raw n string” is a raw string literal.

Boolean literals

A Boolean literal can have any of the two values: True or False.

Example 8: How to use boolean literals in Python?

x = (1 == True)
y = (1 == False)
a = True + 4
b = False + 10

print("x is", x)
print("y is", y)
print("a:", a)
print("b:", b)

Output

x is True
y is False
a: 5
b: 10

In the above program, we use boolean literal True and False. In Python, True represents the value as 1 and False as 0. The value of x is True because 1 is equal to True. And, the value of y is False because 1 is not equal to False.

Similarly, we can use the True and False in numeric expressions as the value. The value of a is 5 because we add True which has a value of 1 with 4. Similarly, b is 10 because we add the False having value of 0 with 10.

Special literals

Python contains one special literal i.e. None. We use it to specify that the field has not been created.

Example 9: How to use special literals in Python?

drink = "Available"
food = None

def menu(x):
    if x == drink:
        print(drink)
    else:
        print(food)

menu(drink)
menu(food)

Output

Available
None

In the above program, we define a menu function. Inside menu, when we set the argument as drink then, it displays Available. And, when the argument is food, it displays None.

Literal Collections

There are four different literal collections List literals, Tuple literals, Dict literals, and Set literals.

Example 10: How to use literals collections in Python?

fruits = ["apple", "mango", "orange"] #list
numbers = (1, 2, 3) #tuple
alphabets = {'a':'apple', 'b':'ball', 'c':'cat'} #dictionary
vowels = {'a', 'e', 'i' , 'o', 'u'} #set

print(fruits)
print(numbers)
print(alphabets)
print(vowels)

Output

['apple', 'mango', 'orange']
(1, 2, 3)
{'a': 'apple', 'b': 'ball', 'c': 'cat'}
{'e', 'a', 'o', 'i', 'u'}

In the above program, we created a list of fruits, a tuple of numbers, a dictionary dict having values with keys designated to each value and a set of vowels.

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