Python Syntax Overview

Executing Python Code

Python syntax can be executed directly in the Command Line interface. For example:

print("Hello, World!")  # Output: Hello, World!

This will output:

Hello, World!

Alternatively, you can create a Python file with the .py extension, save it on your server, and run it via the Command Line:

C:\python myfile.py

Understanding Python Indentation

Indentation refers to the spaces placed at the beginning of a line of code. Unlike many other programming languages where indentation is optional and primarily for readability, Python uses indentation to define the structure of the code. This makes it an essential part of Python syntax.

For example, consider the following code:

if 5 > 2:
    print("Five is greater than two!")  # Output: Five is greater than two!

Here, the indentation indicates that the print statement belongs to the if block. If you omit the indentation, Python will throw a syntax error:

Syntax Error:
if 5 > 2:
print("Five is greater than two!")

The number of spaces used for indentation is flexible, with four spaces being the most common convention. However, it is crucial that all lines within the same block of code have the same indentation level:

if 5 > 2:
    print("Five is greater than two!")  # Output: Five is greater than two!
if 5 > 2:
        print("Five is greater than two!")  # Output: Five is greater than two!

If the indentation is inconsistent within a block, Python will raise an error:

Syntax Error:
if 5 > 2:
    print("Five is greater than two!")
        print("Five is greater than two!")

Working with Python Variables

Variables in Python are created dynamically by assigning a value to them. There is no need for explicit declaration as in some other languages.

For example:

x = 10  # x is an integer with value 10
y = "The Catcher in the Rye"  # y is a string with value "The Catcher in the Rye"

In the above example, x is an integer variable, and y is a string variable. Python automatically determines the type of the variable based on the assigned value.

You’ll learn more about variables in the dedicated chapter on Python Variables.

Using Comments in Python

Comments are essential for in-code documentation and improving code readability. In Python, comments start with a # symbol, and the text following it on the same line is ignored by the interpreter.

For example:

# This is a comment
print("Hello, World!")  # Output: Hello, World!

In this case, # This is a comment is a comment, and Python will not execute it.

Exercises

Now that you’ve learned about Python syntax, indentation, variables, and comments, try creating a simple Python script using these concepts to reinforce your understanding.