How can we identify index of the items in the given list below?

Question

List ={2:5,4:7,5:8}

Answer 1

As Anna said, it's a dictionary, and in this case we speak of "keys", "values" (and "items" for the general term).

try this:
dic ={5:2,2:7,6:8,5:4}
print(dic.keys())
print(dic.values())
print(dic.items())

you will have:
dict_keys([5, 2, 6])
dict_values([4, 7, 8])
dict_items([(5, 4), (2, 7), (6, 8)])

Note the effect of two entries for the key 5, the last one is kept.

Answer 2

Since Python 3.7, dictionaries are insertion-ordered. They will keep the order in which items were inserted.

If I do this in IDLE with Python 3.5.2:

d = {2: 5, 5: 8}

d[4] = 7 # d[4] is inserted last

print(d)

the result is {2: 5, 4: 7, 5: 8} (items are in ascending order, not insertion-ordered).

Output of the same code in Python 3.7.3: {2: 5, 5: 8, 4: 7} (items are insertion-ordered).

You shouldn't rely on a dictionary's indices until you know for sure that Python version >= 3.7 is used (for earlier versions, there is OrderedDict).

Answer 3

That's a dictionary, not a list. Dictionaries don't have indices

Answer 4

Index is the position of an element in the list, starting with 0. If you want to lookup an element and return it's position, use IndexOf(), but this is costly - O(n). If you can asume the list to be sorted, the complexity of IndexOf() will be reduced to O(log n).