Python String Formatting

Bernard Aybout (Virii8)

7 years ago

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Python String Formatting

In Python, you can format strings using C-style string formatting to create new, formatted strings. The “%” operator is used for this purpose. You can use it to format a set of variables, enclosed in a tuple (a fixed-size list), with a format string that contains normal text and “argument specifiers” like %s and %d.

Single Variable Formatting

Let’s start with a simple example where we print a greeting to a user. Suppose you have a variable called name with your username in it.

# This prints out "Hello, John!"
name = "John"
print("Hello, %s!" % name)

Assignment 1:

Create a variable named username with your name and print out “Welcome, [your name]!”

# Write your code here
username = "YourName"
print("Welcome, %s!" % username)

Answer for Assignment 1:

username = "YourName"
print("Welcome, %s!" % username)

Multiple Variable Formatting

To use two or more argument specifiers, use a tuple (enclosed in parentheses).

# This prints out "John is 23 years old."
name = "John"
age = 23
print("%s is %d years old." % (name, age))

Assignment 2:

Create variables first_name and years with your first name and age respectively, and print out “[Your name] is [your age] years old.”

# Write your code here
first_name = "YourName"
years = YourAge
print("%s is %d years old." % (first_name, years))

Answer for Assignment 2:

first_name = "YourName"
years = YourAge
print("%s is %d years old." % (first_name, years))

Formatting Different Types

Any object which is not a string can be formatted using the %s operator. The repr method of the object is used to convert it to a string.

# This prints out: A list: [1, 2, 3]
mylist = [1, 2, 3]
print("A list: %s" % mylist)

Assignment 3:

Create a variable my_numbers with a list of numbers [4, 5, 6] and print “Numbers: [4, 5, 6]”.

# Write your code here
my_numbers = [4, 5, 6]
print("Numbers: %s" % my_numbers)

Answer for Assignment 3:

my_numbers = [4, 5, 6]
print("Numbers: %s" % my_numbers)

Basic Argument Specifiers

Here are some basic argument specifiers you should know:

%s – String (or any object with a string representation, like numbers)
%d – Integers
%f – Floating point numbers
%.2f – Floating point numbers with a fixed number of digits after the decimal point (2 digits in this case)
%x/%X – Integers in hexadecimal representation (lowercase/uppercase)

Comprehensive Example

You will need to write a format string that prints out the data using the following syntax: “Hello John Doe. Your current balance is $53.44.”

# This is the solution.
data = ("John", "Doe", 53.44)
format_string = "Hello %s %s. Your current balance is $%.2f."

print(format_string % data)

Assignment 4:

Create a tuple account_info with the values (“Jane”, “Smith”, 150.75) and print “Hello Jane Smith. Your current balance is $150.75.”

# Write your code here
account_info = ("Jane", "Smith", 150.75)
format_string = "Hello %s %s. Your current balance is $%.2f."
print(format_string % account_info)

Answer for Assignment 4:

account_info = ("Jane", "Smith", 150.75)
format_string = "Hello %s %s. Your current balance is $%.2f."
print(format_string % account_info)

Now that you have practiced basic string formatting in Python, try creating your own formatted strings with different variables and types.

Python String Formatting

Python String Formatting

Single Variable Formatting

Assignment 1:

Answer for Assignment 1:

Multiple Variable Formatting

Assignment 2:

Answer for Assignment 2:

Formatting Different Types

Assignment 3:

Answer for Assignment 3:

Basic Argument Specifiers

Comprehensive Example

Assignment 4:

Answer for Assignment 4:

Python Quick Tip: F-Strings – How to Use Them and Advanced String Formatting

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