Learn Functional Programming in Python/

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Changing Immutable Objects

Changing Immutable Objects

Learn about ways to process immutable data.

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Changing immutable objects

We do sometimes need to “change” immutable objects. Of course, you can’t actually do that, but what you can do is create a copy of the original object, modified in some way. There are various ways of doing this, which we will explore here.

Let’s start with a simple example. The tail function takes a list and returns a list that is identical except that the first term is removed. So, [1, 2, 3] becomes [2, 3]. Here is how we might do this:

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def tail(x): 
  if x: # If x is already empty do nothing 
    del x[0] 
k = [1, 2, 3] 
tail(k) 
print(k) # [2, 3]

This only works for lists. The list is passed into the function and modified in place. But, for reasons we discussed previously, this will fail if we pass a tuple as the parameter. ...

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