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Python: Interpolation

You already know how to move a string or glue several strings together to get a new expression. But there are alternatives to these operations in programming. They make the code more readable and easier to maintain.

The basic way to join strings is concatenation. Using concatenation, the strings are added to each other, as in the example below:

first_name = 'Joffrey'
greeting = 'Hello'

print(greeting + ", " + first_name + "!")
# => Hello, Joffrey!

Concatenation works simply, but doesn't always look so visually clear. The quotation marks make it difficult to see what the end result will be. And the more complex the string is, the more confusing it will start to look. Concatenation has an alternative: interpolation. This is what it looks like:

first_name = 'Joffrey'
greeting = 'Hello'

print(f'{greeting}, {first_name}!')
# => Hello, Joffrey!

The letter f indicates that we are creating an f-string, a pattern into which the value of variables is substituted with the help of curly brackets. The output is a normal string.

Consider this example:

school = 'Hexlet'

what_is_it = f'{school} - online courses'
print(what_is_it)  # => Hexlet - online courses

In almost all languages, interpolation is preferable to concatenation for combining strings. This produces strings that are stuck together, and spaces and characters are visible inside it.

Interpolation helps make code clearer to developers. But that's not the only useful alternative we want to talk about. Later in the course, we'll look at how to declare a multiline string without using \n.


Print the string, Do you want to eat, <name>? Where the variablestarkshould be used instead of`. The output should look like this:

Do you want to eat, Arya?
The exercise doesn't pass checking. What to do? 😶

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In my environment the code works, but not here 🤨

Tests are designed so that they test the solution in different ways and against different data. Often the solution works with one kind of input data but doesn't work with others. Check the «Tests» tab to figure this out, you can find hints at the error output.

My code is different from the teacher's one 🤔

It's fine. 🙆 One task in programming can be solved in many different ways. If your code passed all tests, it complies with the task conditions.

In some rare cases, the solution may be adjusted to the tests, but this can be seen immediately.

I've read the lessons but nothing is clear 🙄

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  • Interpolation a method for obtaining a complex string from several simple ones using special templates

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