Basic Syntax of Python Programming

Basic Syntax

Python shares similarities with other programming languages like Perl, C, and Java, but it also introduces some distinct differences that set it apart. Let’s dive into writing and executing our first Python program, and explore the different modes in which Python can be executed.

First Python Program

Let’s write and execute our 1st Python Program. Python can be executed in different modes:

• Interactive Shell Mode
• Script Mode Programming

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1. Interactive Shell Mode

The Interactive Shell, also known as the Python REPL (Read-Eval-Print Loop), allows you to execute Python code line by line and immediately see the results. This is especially useful for testing small code snippets or experimenting with Python commands.

How to access Interactive Shell Mode?

• Open a terminal (Linux/macOS) or Command Prompt (Windows).
• Type python (or python3 if Python 3 is installed alongside Python 2) and press Enter.

You’ll see a Python prompt >>>, indicating that the Python interpreter is ready to execute commands. Here, the print() function outputs text to the console, and you see the result instantly.

Microsoft Windows [Version 10.0.26100.3775]
(c) Microsoft Corporation. All rights reserved.

C:\Users\ThisPC>python
Python 3.13.3 (tags/v3.13.3:6280bb5, Apr  8 2025, 14:47:33) [MSC v.1943 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> print("Hello World")
Hello World
>>> 5*1
5
>>> 5*2
10
>>> 5*3
15
>>> 5*4
20
>>> 5*5
25
>>> 5*6
30
>>> 5*7
35
>>> 5*8
40
>>> 5*9
45
>>> 5*10
50
>>>exit()
C:\Users\This Pc>

Key features of Interactive Shell Mode:

• Immediate feedback: Every line of code is executed as soon as you press Enter.
• Great for quick calculations, testing functions, or learning Python basics.
• You can exit the shell by typing exit() or pressing Ctrl + D.

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2. Script Mode Programming

In this mode, you write your Python code in a file (with a .py extension) and execute the file. This is typically used for writing complete Python programs. We will use this mode or method throughout this tutorial.

hello.py

  print("Hello World!")

Output

  Hello World!

By this point, I guess we all have the same Question?

How did this .py file got executed by Python? Is python an Interpreted or a Compiled Language?

Note

Internal Working of Python:

Python is an interpreted language. However, it is also partially compiled as Python code is first compiled into bytecode (a lower-level form of code) before being interpreted by the Python Virtual Machine (PVM). This combination of compilation and interpretation makes Python highly flexible and dynamic.

The steps involved in running a Python program are:

• Source code is written in a .py file.
• The Python interpreter compiles the source code into bytecode (.pyc files).
• The bytecode is executed by the Python Virtual Machine (PVM), which interprets it line by line.

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Comments in Python

Comments are used to write something which the programmer does not want to execute. This can be used to mark author name, date etc.

Types of Comments

1. Single Line Comment
   It is used to write a single line comment just add a ‘#’ at the start of the line.

     # This is a Single-Line Comment

2. Multi Line Comment
   Multiline Comments: To write multi-line comments you can use ‘#’ at each line or you can use the multiline string (""" """). It is often referred as Python Doc String, which is important for Python based projects to let other programmers know what the function does. We will know about functions in the upcoming chapters!

     """This is an amazing example of a Multiline comment!"""

   Tip

   When you use triple quotes (""" """ or ''' ''') inside or outside a function, such as within the print () function, it defines a multiline string. The string will retain its format, including line breaks and spacing, and will be printed exactly as it is written.

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Print Function

• The print () function prints the specified message to the screen, or other standard output device.
• The message can be a string, or any other object, the object will be converted into a string before written to the screen.

Syntax:

  print(object(s), sep=separator, end=end, file=file, flush=flush)

Parameter Values:

Parameter	Description
object/ objects	Any object, and as many as you like. Will be converted to string before being printed.
sep	Optional. Specifies how to separate the objects if there is more than one. Default is ' '.
end	Optional. Specifies what to print at the end. Default is '\n' (line feed).
file	Optional. An object with a write method. Default is sys.stdout.
flush	Optional. Boolean. If True, the output is flushed. If False, it is buffered. Default is False.

Examples:

1. Print More Than One Object: You can print multiple objects or strings by separating them with commas.

print("Hello", "how are you?")
# Output: Hello how are you?

2. Print Two Messages with a Custom Separator: The sep parameter lets you specify how multiple objects will be separated in the output.

print("Hello", "how are you?", sep="---")
# Output: Hello---how are you?

3. Print a Variable: You can easily print variables in Python.

x = "Akash"
print(x)
# Output: Akash

4. Multiline String: Python supports multi-line strings using triple quotes (''' or """). This is useful for longer texts or formatting large outputs.

multiline_text = """This is a multiline string.
You can write across multiple lines.
It's very useful for longer outputs."""
print(multiline_text)

5. Formatted Print Statement Using f-strings: With f-strings (formatted string literals), you can embed expressions inside string literals using curly braces {}. This is useful for dynamically displaying values in strings.

name = "Akash"
age = 20
print(f"My name is {name} and I am {age} years old.")
# Output: My name is Akash and I am 20 years old.

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Variables and Data Types

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Variables

• A variable is the name given to a memory location in a program.
• This means that when you create a variable you reserve some space in the memory.

Based on the data type of a variable, Python interpreter allocates memory and decides what can be stored in the reserved memory. Therefore, Python assign’s different data types to variables. For example:

a = 30 # variables = container to store a value.
b = "Akash" # keywords = reserved words in python
c = 71.22 # identifiers = class/function/variable name

Rules for Choosing an identifier / Variable:

A variable can have a short name (like x and y) or a more descriptive name (age, carname, total_volume). Rules for Python variables are:-

• A variable name must start with a letter or the underscore character.
• A variable name cannot start with a number.
• A variable name can only contain alpha-numeric characters and underscores (A-z, 0-9, and _)
• Variable names are case-sensitive (age, Age and AGE are three different variables)
• A variable name cannot be any of the Python keywords.

List of Python keywords:

You can also view this, in the Interactive Shell Mode as discussed Earlier

>>> help()
Welcome to Python 3.13's help utility...Enter the name of any module, keyword, or topic to get help on writing
Python programs and using Python modules...enter "modules spam"...enter "q", "quit" or "exit".

help> keywords

Here is a list of the Python keywords.  Enter any keyword to get more help.

False               class               from                or
None                continue            global              pass
True                def                 if                  raise
and                 del                 import              return
as                  elif                in                  try
assert              else                is                  while
async               except              lambda              with
await               finally             nonlocal            yield
break               for                 not

Examples:

Allowed Variable Names

  myVar = "Akash"
  MYVAR = "Akash"
  myvar2 = "Akash"
  myvar = "Akash"
  my_var = "Akash"
  _my_var = "Akash"

Not Allowed

  2myvar = "John"
  my-var = "John"
  my var = "John"

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Data types

• In general, the data types are used to define the type of a variable. It represents the type of data we are going to store in a variable and determines what operations can be done on it.
• Python data types are actually classes, and the defined variables are their instances or objects.
• Since Python is dynamically typed, the data type of a variable is determined at runtime based on the assigned value.

Built-In Data Types in Python

• Numeric Data Types

  • int
  • flot
  • complex

• String Data Types

• Sequence Data Types

  • list
  • tuple
  • range

• Binary Data Types

  • bytes
  • bytearray
  • memoryview

• Dictionary Data Type

• Set Data Type

  • set
  • frozenset

• Boolean Data Type

• None Data Type

Note

💡Python is a dynamically typed language, meaning it automatically detects the data type of a variable during runtime, based on the value assigned to it. We don’t need to explicitly declare the data type.

a = 71 # identifies a as class <int>
b = 88.44 # identifies b as class <float>
name = "Akash" # identifies name as class <str>

We can also check the type of datatype in python using the type() function like this:

basics.py

  a = 71
  b =88.44
  name = "Akash"
  print (type(a))
  print (type(b))
  print (type(name))

Output

  <class 'int'>
  <class 'float'>
  <class 'str'>

Typecasting - Type Conversion

• Typecasting refers to converting one data type into another. Python allows us to change the type of a variable using built-in functions such as int(), float(), and str().
• However, the conversion is only possible if the content of the variable can logically be converted to the target type.

str (31) =>"31" # integer to string conversion
int ("32") => 32 # string to integer conversion
float (32) => 32.0 # integer to float conversion
#...and so on

Danger

Converting between data types is only possible if the conversion makes logical sense.

int("hello") # This will raise a ValueError because
# string cannot be converted to an integer.

This is because we can’t convert non-numeric strings (e.g., “hello”) into numbers because they don’t represent valid numbers.

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Input Function

• The input() function in Python is used to take user input from the keyboard via the terminal as a string.
• It allows the program to interact with the user, letting them provide data, which is then processed during the execution of the program.

Examples

1. Taking Simple Input & Printing It

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

Output:

Enter your name: Akash
Hello, Akash!

2. Input Data as Strings

The value returned by the input() function is always a string by default, even if the user enters a number.

age = input("Enter your age: ")
print(type(age))  # This will show <class 'str'>

3. Converting Input to Other Data Types

If you want to work with numbers (e.g., for calculations), you’ll need to convert the input into the appropriate data type using typecasting.

• Convert Input to Integer:

age = int(input("Enter your age: "))
print(f"You are {age} years old.")

• Convert Input to Float:

price = float(input("Enter the price: "))
print(f"The price is {price}.")

Tip

Important for Solving Coding Questions

💡Handling Multiple Inputs: Python also allows for taking multiple inputs in one line using the split() method. It take two inputs in a single line and split them into separate variables based on the space between them.

x,y = input("Enter 2 num separated by space: ).split()
print(f"First number: {x}, Second number: {y}")

Output:

Enter 2 num separated by space: 10 20
First number: 10, Second number: 20

📌 Pro Tip:

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