Python Programming

Chapter 1: Modules, Comments & Pip

Let’s write our very first python program.

Create a file called hello.py and paste the below code into it

Execute this file (.py file) by typing python hello.py, and you will see Hello World printed on the screen.

Modules

A module is a file containing code written by somebody else (usually) which can be imported and used in our programs.

Pip

Pip is a package manager for python. You can use pip to install a module on your system.

E.g., pip install flask (It will install flask module in your system)

Types of modules

There are two types of modules in Python:

1. Built-in modules – Pre-installed in Python
2. External modules – Need to install using pip

Some examples of built-in modules are os, abc, etc.

Some examples of external modules are TensorFlow, flask, etc.

Using Python as a Calculator

We can use python as a calculator by typing “python” + TO DO on the terminal. [It opens REPL or read evaluation print loop]

Comments

Comments are used to write something which the programmer does not want to execute.

Comments can be used to mark the author's name, date, etc.

Types of Comments:

There are two types of comments in python,

1. Single line comments – Written using # (pound/hash symbol)
2. Multi-line comments – Written using ’’’ Comment ’’’ or ’”” Comment ’””.

Chapter 1 – Practice Set

1. Write a program to print Twinkle-Twinkle Little Star poem in python.
2. Use REPL and print the table of 5 using it.
3. Install an external module and use it to perform an operation of your interest.
4. Write a python program to print the contents of a directory using os module. Search online for the function which does that.
5. Label the program written in problem 4 with comments.

Chapter 2 – Variables and Data Types

A variable is a name given to a memory location in a program. For example

Variable – Container to store a value

Keywords – Reserved words in Python

Identifiers – class/function/variable name

Data Types:

Primarily there are the following data types in Python:

1. Integers
2. Floating point numbers
3. Strings
4. Booleans
5. None

Python is a fantastic language that automatically identifies the type of data for us.

a = 71                                    #Identifies a as class<int>
  
  b = 88.44                              #Identifies b as class<float>
  
  name = “Raushan”                  #Identifies name as class<Str>

a = 31
  
  type(a)                      #class<int>
  
  b = “31”
  
  type(b)                      #class<str>

Str(31)           # ”31” Integer to string conversion
  
  int(“32”)       # 32 String to int conversion
  
  float(32)       #32.0 Integer to float conversion

a = input(“Enter name”)               #if a is “Raushan”, the user entered Raushan

word = “amazing”
  
  word[1:6:2]           # It will return ’mzn’

word = ‘amazing’
  
  word[:7] or word[0:7]      #It will return ‘amazing’
  
  word[0:] or word[0:7]      #It will return ‘amazing’

len(‘Raushan’)               #Returns 7

letter = ‘’’ Dear <|NAME|>,
  
                          You are selected!
  
                          <|DATE|>

letter = “Dear Raushan, This Python course in nice. Thanks!!”

friends = [‘Apple’, ‘Akash’, ‘Rohan’, 7, False]

L1 = [7, 9, ‘Raushan’]
  
  L1[0] – 7
  
  L1[1] – 9
  
  L1[70] – Error
  
  L1[0:2] – [7,9]         (This is known as List Slicing)

L1 = [1, 8, 7, 2, 21, 15]

a = ()              #It is an example of empty tuple
  
  a = (1,)           #Tuple with only one element needs a comma
  
  a = (1, 7, 2)   #Tuple with more than one element

a = (1, 7, 2)

a = (7, 0, 8, 0, 0, 9)

''' a = {“key”: “value”,
  “Raushan”: “code”,
  “marks” : “100”,
  “list”: [1,2,9]}
  a[“key”]	# Prints value
  a[“list”] 	# Prints [1,2,9] '''
  

a = {“name”: “Raushan”,
      “from”: “India”,
      “marks”: [92,98,96]}

S= Set()          # No repetition allowed!
  
  S.add(1)
  
  S.add(2)
  
  # or Set = {1,2}

S = {1,8,2,3}

S = Set()
  
  S.add(20)
  
  S.add(20.0)
  
  S.add(“20”)

S = {8, 7, 12, “Raushan”, [1, 2]}

'''
  if (condition1):		// if condition 1 is true
      print(“yes”)
  elif (condition2):		// if condition 2 is true
      print(“No”)
  else:				// otherwise
      print(“May be”)
  '''
  

a = 22
  if (a>9):
      print(“Greater”)
  else:
      print(“lesser”)

= = -> equals
  
  >=  -> greater than/equal to
  
  <=, etc.

and -> true if both operands are true else false
  
  or -> true if at least one operand is true else false
  
  not -> inverts true to false and false to true

'''
  if (condition1):
      #code
  elif (condition 2):
      #code
  elif (condition 2):
      #code
  ….
  else:
      #code    '''