Introduction
String formatting in Python is a fundamental skill for creating dynamic and readable strings. Python provides multiple techniques to format strings, such as the format() method, f-strings, and the older %-style formatting. This guide explores these approaches with practical examples and real-world applications.
String Formatting Methods
1. Using the format() Method
The format() method is a versatile way to insert variables into strings.
Syntax
string.format(value1, value2, ...)Example
# Example
name = "Alice"
age = 30
result = "My name is {} and I am {} years old.".format(name, age)
print(result)Output:
My name is Alice and I am 30 years old.
Positional and Keyword Arguments
# Using positional arguments
result = "{0} is learning {1}.".format("Alice", "Python")
# Using keyword arguments
result = "{name} is {age} years old.".format(name="Alice", age=30)
print(result)Output:
Alice is 30 years old.
2. Using F-Strings (Python 3.6+)
F-strings provide a concise and efficient way to format strings using embedded expressions. They are denoted by prefixing the string with f.
Example
# Example
name = "Alice"
age = 30
result = f"My name is {name} and I am {age} years old."
print(result)Output:
My name is Alice and I am 30 years old.
Using Expressions
# Example
result = f"The sum of 5 and 3 is {5 + 3}."
print(result)Output:
The sum of 5 and 3 is 8.
3. Using %-Style Formatting
The % operator provides an older style of string formatting. While it is less commonly used today, it is still worth knowing.
Example
# Example
name = "Alice"
age = 30
result = "My name is %s and I am %d years old." % (name, age)
print(result)Output:
My name is Alice and I am 30 years old.
Advanced String Formatting
Padding and Alignment
# Example
result = "|{:^10}|".format("Python")
print(result)Output:
| Python |
Formatting Numbers
# Example
result = "The value of pi is approximately {:.2f}.".format(3.14159)
print(result)Output:
The value of pi is approximately 3.14.
Interview Questions
- Question 1: What are the advantages of f-strings over the
format()method? - Question 2: How would you format a string to align text to the left, right, or center?
- Question 3: Write a Python program to format a string with dynamic precision for floating-point numbers.
- Question 4: What is the difference between
%-style formatting and f-strings? - Question 5: How can you include curly braces
{}in a formatted string?
Conclusion
String formatting is an essential skill for any Python programmer. Whether you use the format() method, f-strings, or %-style formatting, understanding these techniques will help you write cleaner and more dynamic code. Choose the method that best fits your use case and Python version.