Python Syntax

This article explains Python syntax.

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Syntax in Python

Indentation

Python uses indentation to define blocks of code. Unlike many other languages that use curly braces {} to define code blocks, Python uses indentation. Typically, an indentation of four spaces is used, but tabs can also be used. However, you should be careful not to mix spaces and tabs within a single file.

1x = 5
2if x > 0:
3    print("Positive")
4else:
5    print("Non-positive")

Comments

Single-line comment

In Python, comments begin with #. Everything until the end of the line is treated as a comment.

1# This is a comment
2print("Hello, World!")  # This is also a comment

Documentation string (Docstring)

A docstring is a string used to describe code, enclosed by triple double quotes """ or triple single quotes '''. It is mainly used to describe modules, classes, and functions.

1def greet(name):
2    """
3    This function displays a greeting to the specified name.
4
5    Parameters:
6        name (str): The name of the person to greet.
7    """
8    print(f"Hello, {name}!")

Docstring can be viewed using the help() function.

1help(greet)

Best Practices for Comments

Best practices for comments include the following points:.

 1# Good example
 2# Validate user input and display a personalized message
 3
 4# Ask for the user's name
 5name = input("Enter your name: ")
 6
 7# Ask for the user's age and convert it to an integer
 8age = int(input("Enter your age: "))
 9
10# Check eligibility based on age
11if age >= 18:
12    # Inform the user that they can register
13    print(f"Welcome, {name}! You are eligible to register.")
14else:
15    # Inform the user that they are underage
16    print(f"Sorry, {name}. You must be at least 18 years old to register.")
17
18# Bad example
19# Store the user's name in the variable 'name'
20name = input("Enter your name: ")
21
22# Convert the input to an integer and store it in 'age'
23age = int(input("Enter your age: "))
24
25# Check if the user is greater than or equal to 18
26if age >= 18:
27    # Print a welcome message
28    print(f"Welcome, {name}! You are eligible to register.")
29else:
30    # Print a rejection message
31    print(f"Sorry, {name}. You must be at least 18 years old to register.")

• Be clear and concise Comments are used to clearly explain the intent of the code.

• Do not reiterate the code's meaning Avoid commenting on code that is self-explanatory.

• Maintain consistency In team development, it is important to maintain uniformity in comment style and format.

Variables and Data Types

In Python, you do not need to specify the type when declaring a variable. The type is automatically determined at the time of assignment.

1x = 10        # Integer
2y = 3.14      # Floating-point number
3name = "Alice"  # String (text)
4is_active = True  # Boolean value (True or False)

Conditional Statements

Conditional statements use if, elif (else if), and else.

1x = 0
2if x > 0:
3    print("Positive")
4elif x == 0:
5    print("Zero")
6else:
7    print("Negative")

Loops

Python provides for loops and while loops, each used in different ways.

for Statement

The for statement is typically used to iterate over elements of a list or tuple.

1fruits = ["apple", "banana", "cherry"]
2for fruit in fruits:
3    print(fruit)

while Statement

The while statement repeats a loop as long as the condition is true.

1count = 0
2while count < 5:
3    print(count)
4    count += 1

Defining Functions

In Python, functions are defined using the def keyword.

1def greet(name):
2    print(f"Hello, {name}!")
3
4greet("Alice")

Defining Classes

In Python, you can define classes using the class keyword, enabling object-oriented programming.

1class Dog:
2    def __init__(self, name):
3        self.name = name
4
5    def bark(self):
6        print("Woof!")
7
8dog = Dog("Fido")
9dog.bark()

Modules and Imports

In Python, the import keyword is used to import modules and access existing code.

1# Importing the sqrt function from the math module
2from math import sqrt
3
4result = sqrt(16)
5print(result)  # Output: 4.0

Errors and Exception Handling

Python's try-except structure handles errors and unexpected situations.

1# Catching a division-by-zero error example
2try:
3    result = 10 / 0
4except ZeroDivisionError:
5    print("Cannot divide by zero.")

Conclusion

Python's basic syntax is very simple and highly readable. These basics are essential elements for writing Python code.

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