Python Projects for Beginners a ten-Week Bootcamp Approach to Python Programming

Formatting Strings

Earlier we created a full name by adding multiple strings together to create a larger string. While this is perfectly fine to use, for larger strings it becomes tough to read. Imagine that you had to create a sentence that used 10 variables. Appending all ten variables into a sentence is tough to keep track of, not to mention read. We’ll need to use a concept called string formatting. This will allow us to write an entire string and inject the variables we want to use in the proper locations.

.format( )

The format method works by putting a period directly after the ending string quotation, followed by the keyword “format”. Within the parenthesis after the keyword are the variables that will be injected into the string. No matter what data type it is, it will insert it into the string in the proper location, which brings up the question, how does it know where to put it? That’s where the curly brackets come in to play. The order of the curly brackets is the same order for the variables within the format parenthesis. To include multiple variables in one format string, you simply separate each by a comma. Let’s check out some examples:

# injecting variables using the format method name = "John" print( "Hello { }".format(name) ) print( "Hello { }, you are { } years old!".format(name, 28) )

Go ahead and run that cell. We’ll see that the output in the first line is “Hello John” and the second “Hello John, you are 28 years old”. Keep in mind that the format function will inject variables and even data types themselves. In this instance, we injected the integer value 28.

f Strings (New in Python 3.6)

The new way to inject variables into a string in Python is by using what we call f strings. By putting the letter “f” in front of a string, you’re able to inject a variable into a string directly in line. This is important, as it makes the string easier to read when it gets longer, making this the preferred method to format a string. Just keep in mind you need Python 3.6 to use this; otherwise you’ll receive an error. To inject a variable in a string, simply wrap curly brackets around the name of the variable. Let’s look at an example:

# using the new f strings name = "John" print( f"Hello {name}" )

Go ahead and run the cell. We get the same output that we had gotten with the .format() method; however, it’s much easier to read the code this time.
Note Throughout this book, we’ll be using the .format() method.