How to index into a dictionary?

I have a Dictionary below:

colors = {
    "blue" : "5",
    "red" : "6",
    "yellow" : "8",
}

How do I index the first entry in the dictionary?

colors[0] will return a KeyError for obvious reasons.

Solution 1:

If anybody is still looking at this question, the currently accepted answer is now outdated:

Since Python 3.7*, dictionaries are order-preserving, that is they now behave like collections.OrderedDicts. Unfortunately, there is still no dedicated method to index into keys() / values() of the dictionary, so getting the first key / value in the dictionary can be done as

first_key = list(colors)[0]
first_val = list(colors.values())[0]

or alternatively (this avoids instantiating the keys view into a list):

def get_first_key(dictionary):
    for key in dictionary:
        return key
    raise IndexError

first_key = get_first_key(colors)
first_val = colors[first_key]

If you need an n-th key, then similarly

def get_nth_key(dictionary, n=0):
    if n < 0:
        n += len(dictionary)
    for i, key in enumerate(dictionary.keys()):
        if i == n:
            return key
    raise IndexError("dictionary index out of range") 

* CPython 3.6 already included insertion-ordered dicts, but this was only an implementation detail. The language specification includes insertion-ordered dicts from 3.7 onwards.

Solution 2:

Dictionaries are unordered in Python versions up to and including Python 3.6. If you do not care about the order of the entries and want to access the keys or values by index anyway, you can create a list of keys for a dictionary d using keys = list(d), and then access keys in the list by index keys[i], and the associated values with d[keys[i]].

If you do care about the order of the entries, starting with Python 2.7 you can use collections.OrderedDict. Or use a list of pairs

l = [("blue", "5"), ("red", "6"), ("yellow", "8")]

if you don't need access by key. (Why are your numbers strings by the way?)

In Python 3.7, normal dictionaries are ordered, so you don't need to use OrderedDict anymore (but you still can – it's basically the same type). The CPython implementation of Python 3.6 already included that change, but since it's not part of the language specification, you can't rely on it in Python 3.6.

Solution 3:

If you need an ordered dictionary, you can use odict.

Solution 4:

Addressing an element of dictionary is like sitting on donkey and enjoy the ride.

As a rule of Python, a DICTIONARY is orderless

If there is

dic = {1: "a", 2: "aa", 3: "aaa"}

Now suppose if I go like dic[10] = "b", then it will not add like this always

dic = {1:"a",2:"aa",3:"aaa",10:"b"}

It may be like

dic = {1: "a", 2: "aa", 3: "aaa", 10: "b"}

Or

dic = {1: "a", 2: "aa", 10: "b", 3: "aaa"}

Or

dic = {1: "a", 10: "b", 2: "aa", 3: "aaa"}

Or any such combination.

So a rule of thumb is that a DICTIONARY is orderless!