Python String format() Method
Last Updated :
11 Jul, 2025
format() method in Python is a tool used to create formatted strings. By embedding variables or values into placeholders within a template string, we can construct dynamic, well-organized output. It replaces the outdated % formatting method, making string interpolation more readable and efficient. Example:
Python
a = "shakshi" # name
b = 22 # age
msg = "My name is {0} and I am {1} years old.".format(a,b)
print(msg)
OutputMy name is shakshi and I am 22 years old.
Explanation: format(a, b) method replaces {0} with the first argument (a = "shakshi") and {1} with the second argument (b = 22).
String Format() Syntax
string.format(value1, value2, ...)
Parameter: values (such as integers, strings, or variables) to be inserted into the placeholders in the string.
Returns: a string with the provided values embedded in the placeholders.
Using a single placeholder
A single placeholder {} is used when only one value needs to be inserted into the string. The format() method replaces the placeholder with the specified value.
Python
# using a single placeholder
print("{}, a platform for coding enthusiasts.".format("GeeksforGeeks"))
# formatting with a variable
a = "Python"
print("This article is written in {}.".format(a))
# formatting with a number
b = 18
print("Hello, I am {} years old!".format(b))
OutputGeeksforGeeks, a platform for coding enthusiasts.
This article is written in Python.
Hello, I am 18 years old!
Using multiple placeholders
When a string requires multiple values to be inserted, we use multiple placeholders {}. The format() method replaces each placeholder with the corresponding value in the provided order.
Syntax:
"{ } { }".format(value1, value2)
Parameters:
- Accepts integers, floats, strings, characters, or variables.
Note: The number of placeholders must match the number of values provided.
Example:
Python
# Using multiple placeholders
print("{} is a {} science portal for {}.".format("GeeksforGeeks", "computer", "geeks"))
# Formatting different data types
print("Hi! My name is {} and I am {} years old.".format("User", 19))
# Values replace placeholders in order
print("This is {} {} {} {}.".format("one", "two", "three", "four"))
OutputGeeksforGeeks is a computer science portal for geeks.
Hi! My name is User and I am 19 years old.
This is one two three four.
String format() IndexError
Python assigns indexes to placeholders {0}, {1}, {2}, .... If the number of placeholders exceeds the provided values, an IndexError occurs.
Example:
Python
s = "{}, is a {} {} science portal for {}"
print(s.format("GeeksforGeeks", "computer", "geeks")) # Missing one argument
Output
Hangup (SIGHUP)
Traceback (most recent call last):
File "/home/guest/sandbox/Solution.py", line 2, in <module>
print(s.format("GeeksforGeeks", "computer", "geeks")) # Missing one argument
~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
IndexError: Replacement index 3 out of range for positional args tuple
Escape Sequences in Strings
We can use escape sequences to format strings in a more readable way. Escape sequences allow us to insert special characters such as newline \n, tab \t, or quotes.
| Escape sequence | Description | Example |
|---|
| \n | Breaks the string into a new line | print('I designed this rhyme to explain in due time\nAll I know') |
| \t | Adds a horizontal tab | print('Time is a \tvaluable thing') |
| \\ | Prints a backslash | print('Watch it fly by\\as the pendulum swings') |
| \' | Prints a single quote | print('It doesn\'t even matter how hard you try') |
| \" | Prints a double quote | print('It is so\"unreal\"') |
| \a | makes a sound like a bell | print('\a') |
Positional and Keyword Arguments in format
In Python, {} placeholders in str.format() are replaced sequentially by default. However, they can also be explicitly referenced using index numbers (starting from 0) or keyword arguments.
Syntax:
"{0} {1}".format(positional_argument, keyword_argument)
Parameters : (positional_argument, keyword_argument)
- Positional_argument can be integers, floating point numeric constants, strings, characters and even variables.
- Keyword_argument is essentially a variable storing some value, which is passed as parameter.
Example:
Python
# Positional arguments (placed in order)
print("{} love {}!!".format("GeeksforGeeks", "Geeks"))
# Changing order using index
print("{1} love {0}!!".format("GeeksforGeeks", "Geeks"))
# Default order in placeholders
print("Every {} should know the use of {} {} programming and {}".format("programmer", "Open", "Source", "Operating Systems"))
# Reordering using index
print("Every {3} should know the use of {2} {1} programming and {0}".format("programmer", "Open", "Source", "Operating Systems"))
# keyword arguments
print("{gfg} is a {0} science portal for {1}".format("computer", "geeks", gfg="GeeksforGeeks"))
OutputGeeksforGeeks love Geeks!!
Geeks love GeeksforGeeks!!
Every programmer should know the use of Open Source programming and Operating Systems
Every Operating Systems should know the use of Source Open p...
Formatting with Type Specifiers
Python allows specifying the type specifier while formatting data, such as integers, floating-point numbers, and strings. This is useful for controlling the display of numeric values, dates and text alignment.
Example:
Python
product, brand, price, issue, effect = "Smartphone", "Amazon", 12000, "bug", "troubling"
print("{:<20} is a popular electronics brand.".format(brand))
print("They have a {} for {} rupees.".format(product, price))
print("I wondered why the program was {} me—turns out it was a {}.".format(effect, issue))
print("Truncated product name: {:.5}".format(product))
OutputAmazon is a popular electronics brand.
They have a Smartphone for 12000 rupees.
I wondered why the program was troubling me—turns out it was a bug.
Truncated product name: Smart
Explanation:
- %-20s left-aligns the brand name within 20 spaces.
- %s inserts strings dynamically.
- %d formats integers properly.
- %.5 truncates the product name to the first 5 characters.
Another useful Type Specifying
Specifier | Description |
|---|
%u | unsigned decimal integer |
|---|
%o | octal integer |
|---|
%f | floating-point display |
|---|
%b | binary number |
|---|
%x | hexadecimal lowercase |
|---|
%X | hexadecimal uppercase |
|---|
%e | exponent notation |
|---|
We can specify formatting symbols using a colon (:) instead of %. For example, instead of %s, use {:s}, and instead of %d, use {:d}. This approach provides a more readable and flexible way to format strings in Python.
Example:
Python
print("This site is {:.6f}% securely {}!!".format(100, "encrypted"))
# To limit the precision
print("My average of this {} was {:.2f}%".format("semester", 78.234876))
# For no decimal places
print("My average of this {} was {:.0f}%".format("semester", 78.234876))
# Convert an integer to its binary or other bases
print("The {} of 100 is {:b}".format("binary", 100))
print("The {} of 100 is {:o}".format("octal", 100))
OutputThis site is 100.000000% securely encrypted!!
My average of this semester was 78.23%
My average of this semester was 78%
The binary of 100 is 1100100
The octal of 100 is 144
Explanation:
- {0:f}: Floating-point representation.
- {1:.2f}: Floating-point with two decimal places.
- {1:.0f}: Rounds the floating number to the nearest integer.
- {1:b}: Converts integer to binary.
- {1:o}: Converts integer to octal.
Type Specifying Errors
When explicitly converted floating-point values to decimal with base-10 by 'd' type conversion we encounter Value-Error.
Example:
Python
print("The temperature today is {:d} degrees outside !".format(35.567))
Output
ValueError: Unknown format code 'd' for object of type 'float'
# Instead write this to avoid value-errors
Python
print("The temperature today is {:.0f} degrees outside !".format(35.567))
OutputThe temperature today is 36 degrees outside !
Handling large data with formatting
Formatters are generally used to Organize Data. If we are showing databases to users, using formatters to increase field size and modify alignment can make the output more readable.
Example: Organizing numerical data
Python
def formatted_table(a, b):
for i in range(a, b):
print("{:6d} {:6d} {:6d} {:6d}".format(i, i**2, i**3, i**4))
formatted_table(3, 10)
Output 3 9 27 81
4 16 64 256
5 25 125 625
6 36 216 1296
7 49 343 2401
8 64 512 4096
9 81 729 6561
Explanation: The formatted_table function prints a table of numbers from a to b-1, displaying each number along with its square, cube, and fourth power. It formats the output with each value taking up 6 spaces for clean alignment.
Using a dictionary for formatting
Using a dictionary to unpack values into the placeholders in the string that needs to be formatted. We basically use ** to unpack the values. This method can be useful in string substitution while preparing an SQL query.
Python
d = {"first_name": "Tony", "last_name": "Stark", "aka": "Iron Man"}
print("My name is {first_name} {last_name}, also known as {aka}.".format(**d))
OutputMy name is Tony Stark, also known as Iron Man.
Explanation: format(**d) method unpacks the dictionary d, replacing the named placeholders with corresponding values, resulting in a formatted string.
Python format() with list
Given a list of float values, the task is to truncate all float values to 2 decimal digits. Let’s see the different methods to do the task.
Python
a = [100.7689454, 17.232999, 60.98867, 300.83748789]
# Using format
b = ['{:.2f}'.format(elem) for elem in a]
print(b)
Output['100.77', '17.23', '60.99', '300.84']
Explanation: list comprehension rounds each element in a to two decimal places, creating a list of formatted strings in b.
Explore
Python Fundamentals
Python Data Structures
Advanced Python
Data Science with Python
Web Development with Python
Python Practice