why dict does not have remove method?

Question

I know python list has a remove() method, which remove the given object from the list.

aList = [123, 'xyz', 'zara', 'abc', 'xyz']
aList.remove('xyz')

I know that we can use del statement to delete an item from the list by offset:

del aList[-1]

I also know that we can use del statement to delete an item from the dictionary by key:

aDict = {'a':1, 'b':2 'c':3}
del aDict['a']

However, there is no remove() method for a dictionary, which I think is perfectly fine:

aDict.remove('a')

I guess one reason is that remove() does not save any typing than del statement for dictionary, so it is not necessary. Is this correct?

While for list, remove() combines "search index by value" and "delete by index" together, so it has to be there. Is this correct?

What are the other reasons if any?

Answer 1

Dictionaries have pop, but not remove. Why not? Because remove finds the first matching value and removes it, and returns nothing. So in a dictionary:

{'a': 5, 'b': 5}

dict.remove ought to remove values. If I use dict.remove(5), which key should it delete? Additionally this is not even very useful operation. If you need to remove a certain value from a dictionary, then you're using a wrong data structure.

---

dct.pop(key)

on the other hand, is not unlike

value = dct[key]
del dct[key]
return value

This can be contrasted with pop method of lists:

lst.pop(index)

is analogous to

value = lst[index]
del lst[index]
return value

that is, both of them operate using the same principle.

Answer 2

Note that list.remove makes a very strict guarantee - removing the first occurrence of a value. Now, the ordering in a dict is arbitrary - there is no "first".

Answer 3

If you look at this question: Difference between del, remove and pop on lists : you'll note the main answer points out

remove: removes the first matching value, not a specific index

del: removes a specific index

pop: returns the removed element

So with a Dictionary it simply doesn't need a remove method as there can only be one instance of a key (they have to be unique) and del is sufficient.

Answer 4

It does, it's just called pop:

pop(key[, default])
If key is in the dictionary, remove it and return its value, else return default. If default is not given and key is not in the dictionary, a KeyError is raised.