Python string format

Python 數值字串處理

When you google `python format`, you’ll see a lot of articles. Here I want to make a short summary and present the formatting methods in a proper way.
Chinese version is on my blog already: Python Handling Strings

In general, there are three ways: %, .format(), and f-string. We’ll discuss their use and give examples for you.

% operator

This is the oldest way to format your string and this should go with print() function. The placeholder is your % followed by the format.

• %d: decimal
• %o: octal
• %x: octal
• %e: exponential
• %f: floats
• %s: string

In our examples, you can see the % plays as a placeholder in the print function. and what after % is the rule to format your input. However, if you have a long string to format, you have to type many % and it becomes hard to understand each variable. The readability is terrible.

.format()

In python 2+, .format() method is released. It provides better readability and thus a cleaner way to format.

Now the placeholder is {} with the format inside. Because now you can have variables inside the {}, it enhances the flow to read one’s code. However, again, the if there are tons of inputs, the format function would be incredibly long.

f-string

Fancier Output Formatting (according to python documents). This formatting method started in python 3.6 and it provides the best format readability.

The placeholder remains to be {} but we don’t have to add .format at the end. Instead, the variable can be put inside the {} intuitively.

What to be noted is that combining raw string and f string may be a good way in your code. Because things like ‘\n’ would be different in raw string and f-string.

Take home message

if your program requires to print a lot of information of your variables, f-string is your good friend, especially using f’’’ ‘’’ to print a paragraph. It saves a lot of time to track each variable in the string. But one uses f-string should take care of the characters like \n we mentioned.