Python String Formatting
String formatting comes into the picture when we want to insert items into the string. For example:
first_name = "Steve"
id = 5
print(first_name +", your ID is " + str(id) + ".")
The above approach is inefficient if we insert too many variables into the string. Especially, in the case of integers and floats, they all have to be converted into strings. So, we have a few other methods.
We can perform string formatting using any of these:
- String Formatting Operator(%)
- .format() method
- f-string
- Template Strings
String Formatting Operator(%)
The symbol % is known as the string formatting operator. This symbol is used with other characters to insert various types of values. For example, we can use %s for string and %f for floating-point numbers.
%s is used to insert a value as a string.
print("How are you %s." %'Steve')
first_name = "Steve"
last_name = "Jobs"
print("How are you %s %s." %(first_name, last_name))
%d is used to insert a value as an integer.
bill = 54.98
print("Your bil is %s" %bill)
print("Your bil is %d" %bill)
% for width and alignment
%f is used to insert a value as a float.
bill = 54.98
print("Your bill is %f" %bill)
Total 12 numbers and 4 after decimal.
bill = 54.98
print("Your bill is %12.4f" %bill)
Total 12 numbers and 0 after decimal.
bill = 54.98
print("Your bill is %12.0f" %bill)
format() method
The format() method improves the string formatting operator. The format method is called after the string, and the items are passed as parameters to the format method. Curly brackets are used as the placeholders inside the string.
Curly bracket as placeholder.
print("Hello {}, {} was calling you and {}.".format("Steve","Bill", "Tim"))
We can use index position of arguments also, which starts from 0.
print("Hello {1}, {0} was calling you and {2}.".format("Steve","Bill", "Tim"))
We can assign keys to arguments also, like s, b and t assigned below. This key is used in placeholder.
print("Hello {t}, {b} was calling you and {s}.".format(s = "Steve",b = "Bill", t = "Tim"))
format() for width and alignment
Simply printing float.
bill = 54.98
print("Your bill is {}".format(bill))
Width of 8.
bill = 54.98
print("Your bill is {:8}.".format(bill))
Width of 8 and left aligned.
bill = 54.98
print("Your bill is {:<8}.".format(bill))
Width of 8 and 4 after decimal.
bill = 54.98
print("Your bill is {:8.4f}.".format(bill))
f-strings
The f-strings are the advancement of the format() method. The ‘f’ is used at the beginning of the string, and we can put items at the placeholder.
first_name = "Steve"
last_name = "Jobs"
print(f"How are you {first_name} {last_name}.")
f-string for width and alignment
bill = 54.98
print(f"Your bil is {bill}")
bill = 54.98
print(f"Your bil is {bill:10.5f}")
Template String
Template strings are a feature introduced in Python 3.6 through the string module. They provide a simplified syntax for string formatting, making it more readable. Unlike other string formatting methods like % formatting or str.format(), template strings use a simple syntax that aligns with the principles of readability and simplicity.
Simple use of Template String
from string import Template
name = "Steve"
age = 45
template = Template("My name is $name, and I am $age years old.")
result = template.substitute(name=name, age=age)
print(result)
