Python Comments

In the previous tutorial, you learned to write your first Python program. Now, let's learn about Python comments.

Tip: We are introducing comments early in this tutorial series because, from now on, we will be using them to explain our code.

In Python, parts of code beginning with # are called comments. For example,

# print a number
print(25)

Here, # print a number is a comment. As such, it is completely ignored by the computer.

Comments are hints that we add to our code to make it easier to understand.

Note: You can ignore the programming concepts and simply focus on the comments. We will revisit these concepts in later tutorials.

Single-line Comment

We use the hash (#) symbol to write a single-line comment. For example,

# declare a variable
name = 'John'

# print name
print(name)    # John

In the above example, we have used three single-line comments:

• # declare a variable
• # print name
• # John

We can also use single-line comments alongside the code:

print(name)    # John

Note: Remember the keyboard shortcut to apply comments. In most text editors, it's Ctrl + / if you are on Windows & Cmd + / if you are on a Mac.

Multiline Comments

Unlike languages such as C++ and Java, Python doesn't have a dedicated method to write multi-line comments.

However, we can achieve the same effect by using the hash (#) symbol at the beginning of each line.

Let's look at an example.

# print(1)
# print(2)
# print(3)

We can also use multiline strings as comments like:

'''This is an example 
of multiline comment'''
print("Hello World")

Output

Hello World

We can see that these unassigned multiline strings are ignored.

Prevent Executing Code Using Comments

Comments are valuable when debugging code.

If we encounter an error while running a program, instead of removing code segments, we can comment them out to prevent execution.

For example,

number1 = 10
number2 = 15

sum = number1 + number2

print('The sum is:', sum)
print('The product is:', product)

Here, the code throws an error because we have not defined a product variable.

We can comment out the code that's causing the error.

For example,

number1 = 10
number2 = 15

sum = number1 + number2

print('The sum is:', sum)
# print('The product is:', product)

Output

The sum is 25

Now, the code runs without any errors.

Here, we have resolved the error by commenting out the code related to the product.

If we need to calculate the product in the near future, we can uncomment it.

Why Use Comments?

We should use comments for the following reasons:

• Comments make our code readable for future reference.
• Comments are used for debugging purposes.
• We can use comments for code collaboration as it helps peer developers to understand our code.

Next, we will be learning about Python variables and literals.