Question

When I introduce new pair it is inserted at the beginning of dictionary. Is it possible to append it at the end?

Answer 1

UPDATE

As of Python 3.7, dictionaries remember the insertion order. By simply adding a new value, you can be sure that it will be “at the end” if you iterate over the dictionary.

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Dictionaries have no order, and thus have no beginning or end. The display order is arbitrary.
If you need order, you can use a list of tuples instead of a dict:

In [1]: mylist = []

In [2]: mylist.append(('key', 'value'))

In [3]: mylist.insert(0, ('foo', 'bar'))

You’ll be able to easily convert it into a dict later:

In [4]: dict(mylist)
Out[4]: {'foo': 'bar', 'key': 'value'}

Alternatively, use a collections.OrderedDict as suggested by IamAlexAlright.