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Python: Default Arguments

Let's look at the round() function, which rounds the number passed to it:

result = round(10.25, 0)  # 10.0

We passed two parameters to it:

  • Number to be rounded
  • Rounding accuracy

0 means that the rounding will be to an integer value. More often than not, you need to round to a whole number, not to two, three, four etc. decimal places. So the creators of the round function made the second parameter unnecessary and gave it a default value of 0 inside the function. So, you can choose to not specify the second parameter and the result will be the same:

result = round(10.25)  # 10.0

And if you need a different precision, you can pass a parameter:

# rounding to one decimal place
result = round(10.25, 1)  # 10.2

If a function in Python accepts optional arguments, they always come after the mandatory ones. There can be any number of them. It depends on the function itself, but they always go next to and at the end of the list of arguments.


Round up the number written in the number variable to two decimal places and print the result on the screen.

The exercise doesn't pass checking. What to do? 😶

If you've reached a deadlock it's time to ask your question in the «Discussions». How ask a question correctly:

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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.

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  • Default setting optional function parameter

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