Summary: f-string
is more readable and easier to implement than %
and .format()
string formatting styles. Furthermore, using f-strings
is suggested for Python 3.6 and above while .format()
is best suited for Python 2.6 and above. Versions prior to Python 2.6 only provide %
option for string formatting. In terms of speed, %
is the fastest string formatting style.
Overview
Problem: Compare the different string formatting styles in Python i.e. %
Vs .format()
Vs Formatted String Literal/f-strings
.
Solution Overview: There are 4 ways of formatting a string in Python as of now. These are
%
formattingstr.format()
f-string
(String Literal)- Template Strings
Example: Let us have a look at the following example where we have used all the four ways of string formatting:
from string import Template name = "FINXTERS!" print('1. Hello %s' % name) print('2. Hello {}'.format(name)) print(f"3. Hello {name}") temp = Template("4. Hello $name") print(temp.substitute(name=name))
Output
1. Hello FINXTERS! 2. Hello FINXTERS! 3. Hello FINXTERS! 4. Hello FINXTERS!
So, from the above example, we see that all the string formatting types produce the same output. Having said that, we now have a lot of questions to address. Some of these questions include :
- What is the difference between each string formatting method?
- Which string formatting method should be preferred and in which situation should it be preferred?
To learn more about the usage of each Python string formatting, follow this blog tutorial. However, in this article, we will learn and primarily focus on the key differences between the first three string formatting methods as mentioned in our problem statement. Without further delay let us dive into the key differences.
Before you dive deeper into these methods, let’s make it stick with this quick exercise:
Exercise: Add a second string variable firstname
and insert it into each output!
Syntax Difference
The following table depicts the difference in syntax between each string formatting method:
% formatting | str.format() | f-Strings |
Syntax: <string with format specifier>%variable | Syntax: <string with placeholder> .format(value1, value2…) | Syntax: f'<string with its placeholder>’ |
example: name = “FINXTERS!” print(‘1. Hello %s’ % name) | example: name = “FINXTERS!” print(‘2. Hello {}’.format(name)) | example: name = “FINXTERS!” print(f’3. Hello {name}’) |
Version And Compatibility Difference
The following table depicts the difference between each string formatting style in terms of their compatibility in different Python versions.
% formatting | str.format() | f-Strings |
1. Introduced in the initial/first release of Python. | 1. Introduced in Python 2.6. | 1. Introduced in Python 3.6. |
2. Can be used in any version of Python. However, it is not a recommended style of string formatting for Python 2.6 and above. | 2. It can be used in Python 2.6 and above. However, it will raise a syntax error if used in versions prior to Python 2.6. | 2. Can be used only in Python 3.6 and above. It will raise a Syntax Error if used in versions prior to Python 3.6 |
Functional Difference
% formatting | str.format() | f-Strings |
% is an operator known as modulo operator which allows us to format a string object in Python. | It is an inbuilt method that allows us to format a string object in Python. | f-string is a literal string in Python, with 'f' as a prefix and contains expressions inside braces. |
Complex syntax and can either accept a variable or a tuple. Please have a look at Example 1 given below, to get a better view of this concept. | Being a newer and improved string formatting style it is more versatile and easy to use than % . It has a simpler syntax and uses similar syntax whether you need to accept a string variable or a tuple. Please have a look at Example 1 given below, to get a better view of this concept. | It uses an even simpler syntax since .format() can get tedious, especially when used with long strings. Please have a look at Example 1 given below, to get a better view of this concept.It is a more powerful option of string formatting on account that it allows us to embed expressions within the string itself. Please have a look at Example 2 given below to get a better view of this concept. |
Let us compare the string formatting styles based on their ease of implementation using a few examples:
Example 1
name = 'Finxter Shubham' tup = (1, 2, 3) # Different syntax for printing a string and tuple print("Name: %s" % name) print("Tuple: %s" % (tup,)) # same syntax to print both string and tuple print("Name: {}".format(name)) print("Tuple: {}".format(tup)) # even more readable and easier syntax print(f'Name: {name}') print("Tuple: " f'{tup}')
Output
Name: Finxter Shubham Tuple: (1, 2, 3) Name: Finxter Shubham Tuple: (1, 2, 3) Name: Finxter Shubham Tuple: (1, 2, 3)
f-strings
lead to cleaner code because their syntax enables the value of an expression to be placed directly inside a string. The following example shows how to easily embed expressions within f-strings
:
Example 2
# The number of units per player units = {} units['Alice'] = 10 units['Bob'] = 15 x = 'Alice' y = 'Bob' print(f'{x} has {units["Bob"] - units["Alice"]} units less than {y}')
Output
Alice has 5 units less than Bob
To find out, how you can perform the above operation in the .format()
string formatting method – click here!
► Now, let us have a look at an example that depicts how easily we can use positional arguments in case of .format()
and f-strings
but how hideous it becomes while doing the same using %
formatting.
Example 3
tu = (100, 500, 300) print('{0} {2} {1}'.format(*tu)) print(f'{tu[0]}, {tu[2]}, {tu[1]}') # using % formatting print('%(a)s %(c)s %(b)s' % {'a': 100, 'b': 500, 'c': 300})
Output
100 300 500 100, 300, 500 100 300 500
► Another advantage of the new string formatting methods over %
string formatting is :- new styles can take object properties whereas %
cannot do so. Let us have a look at the following code to see the working principle behind this concept:
class Finxter(object): def __init__(self, a, b): self.x = a self.y = b a = Finxter(2, 3) print("\nUsing .format():") print('Value1 = {0}\nValue2 = {1}'.format(a.x, a.y)) print("\nUsing f-string:") print(f'Value1={a.x}\nValue2={a.y}') print("\nNot possible using %")
Output
Using .format(): Value1 = 2 Value2 = 3 Using f-string: Value1=2 Value2=3 Not possible using %
Speed/Performance Difference
Though speed and performance are not the primary metrics when it comes to string formatting yet we must discuss the difference between them in terms of performance since there might be a rare situation where speed is also a criteria in the program.
Let us have a look at the following program to discover who wins the race in terms of speed:
import timeit print('.format() Speed:', timeit.timeit("'{}{}{}'.format(0.5, 1.5, 'SPEED TEST!')")) print('% Speed:', timeit.timeit("'%s%s%s' % (0.5, 1.5, 'SPEED TEST!')")) print('f-string Speed:', timeit.timeit("f'{0.5}{1.5}{\"SPEED TEST!\"}'"))
Output
.format() Speed: 1.615438 % Speed: 1.2333532999999999 f-string Speed: 1.2435527000000004
Therefore, we see that %
(modulo) string formatting style wins the performance race!
Use Case That Suits A Specific String Formatting Style
From the above discussions, we can easily deduce the following:
- If you are using any version prior to Python 2.6 stick with the old
%
(modulo) string formatting method. - If you are using Python 2.6 or above then using the
.format()
string formatting method is a better option. - If you are using Python 3.6 or above, the best option for string formatting is
f-string
.
If you are confused regarding the version of Python you are working upon, then you might want to have a look at this tutorial.
Conclusion
In this article, we discussed the key differences between %
, str.format
(), and f-strings
based on numerous factors along with their examples. I hope after reading this article you can compare and contrast the differences between each string formatting style with ease. Though the examples used in the above article are very basic ( for a better understating of the concept), the same contrasts also hold true in the case of complex situations.
If you enjoyed reading this article, please subscribe and stay tuned for more interesting articles!
Where to Go From Here?
Enough theory. Let’s get some practice!
Coders get paid six figures and more because they can solve problems more effectively using machine intelligence and automation.
To become more successful in coding, solve more real problems for real people. That’s how you polish the skills you really need in practice. After all, what’s the use of learning theory that nobody ever needs?
You build high-value coding skills by working on practical coding projects!
Do you want to stop learning with toy projects and focus on practical code projects that earn you money and solve real problems for people?
🚀 If your answer is YES!, consider becoming a Python freelance developer! It’s the best way of approaching the task of improving your Python skills—even if you are a complete beginner.
If you just want to learn about the freelancing opportunity, feel free to watch my free webinar “How to Build Your High-Income Skill Python” and learn how I grew my coding business online and how you can, too—from the comfort of your own home.