Introduction to String Formatting in Python
String formatting can be defined as the method used for formatting the string present or provided as input in the program, which formats the characters when executed. This function is employed for declaring, accessing and updating the string variables for formatting purposes. In Python, this function is attained by a particular method, which can be implemented using the syntax ‘{string variable}.format(value)’. Here, ‘value’ represents the data in any format like numbers, characters, or floating points. The different types of string formatting applied in the python programming are single formatter, multiple formatter, formatter with positional and keyword arguments, and index error.
How to Format String in Python?
This is the most important part of this article which is an answer to the above question. It is not that hard to format string in python as we can use a format method in Python3 for formatting. The function is easy to use. We will take a look at the syntax of this function.
Syntax:
{string variable}.format(value)
So, in place of the value, we can put any string, number characters, and even other variables. This method returns a formatted string.
There are few ways to do string formatting in python. We will look into this one by one.
1. Single Formatter
This means we pass only one parameter inside the format function which places the value passed as a parameter in the placeholder position. The placeholder position is represented by curly braces. Since we are passing only one parameter inside the format function. It is called a single formatter. To understand better we will use Jupyter notebook to look at the output.
Code:
#program to demonstrate single Formatter in Python3
#format option for value stored in a variable
str = "Rahul is a nice {}"
print(str.format("boy"))
#format option for simple string
print("Who is inside my {}".format("house"))
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So, if we look at the code we have used two cases in the first case we are assigning the string to a variable whereas in the second case we are directly using the format function on the string.
Output:
As you can see in both cases we get the placeholders replaced by the values passed as a parameter with the format function.
2. Multiple Formatters
In this case, the format method will have more than one parameter in it. This type of formatting is used when we want to do more than one variable substitution in the existing string. We will have to place extra placeholders in the string if we want to do more than one variable substitution. The placeholders will be replaced by values in order. For example, if we want to substitute two values in a string then we need to place two placeholders and pass two arguments inside the format function. Let us see the code of an example.
Code:
#program to demonstrate Multiple Formatter in Python3
#format option for value stored in a variable
str = "Rahul is a nice {} and he is {}"
print(str.format("boy","young"))
#format option for simple string
print("This is {} and lots of {}".format("great","fun"))
The above code has two cases in the first case we are assigning the string to a variable whereas in the second case we are directly using the format function on the string.
Output:
As you can see in both cases we get both the placeholders replaced by the values passed as a parameter with the format function and the values are substituted in order which is very important to remember.
3. Formatters with Positional and Keyword Arguments
This is an interesting way of formatting using the string formatter. To understand this we will have to understand that values placed as parameters inside the format function have tuple as their data type which means they can be individually called using their index number starting from zero. These index numbers can be passed in the placeholders of the original string and based on the index number the values will be substituted in the placeholders. We will use a sample code for better understanding. Let us look at the code.
Code:
# formatters with positional key arguments.
# Positional arguments placed in order
print("{0} likes {1}!!".format("Ram","Radha"))
# Reverse the index numbers
print("{1} likes {0}!!".format("Ram","Radha"))
# Keyword arguments along with index
print("{name} likes {0}!!".format("Radha",name ="Ram"))
If you look at the above code we can see we have used three cases in the first two cases we have used index numbers in placeholders. The only difference between the first two cases is the reverse order of index numbers but in the third case, we have actually used a keyword which basically means a variable whose value we assign inside the format function. We are not only using index so you can see the index is zero as the first placeholder is substituted using the value of the variable passed inside the format function.
Output:
The screenshot output shows us the different cases where we can use this type of string formatting.
4. Index Error
It is important to discuss this as we should remember that there is something we get as an index error when the number of placeholders passed in a string does not match with the number of parameters inside the format function. So we would, for example, get index error if we have three placeholders for two parameters in the format method.
Code:
str = "Rahul is a nice {} and he is {},{}"
print(str.format("boy","young"))
As you can see we have an extra placeholder.
Output:
As you can see we get an index error with the message “tuple index out of range”.
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This is a guide to String Formatting in Python. Here we discuss the concept and how to format string in python with code implementation. You may also look at the following articles to learn more –
