PYTHON

Let's check out some important functions that are quite helpful when we are playing around with dictionaries in python.

As you might have already guessed, it gives the number of elements stored in the dictionary or you can say just the number of keys in it.

`>>> len(myDictionary)`

5

If we ever need to delete all elements of the dictionary using the `del`

keyword, for each **key** value, that would be quite troublesome. Hence `clear()`

function makes emptying a dictionary, a single line task.

```
>>> myDictionary.clear()
>>> myDictionary
```

{}

Suppose you don't want to access the **keys** while displaying the value stored in the dictionaries, then `values()`

function can be used. This function will show all the values stored in the dictionary.

`>>> myDictionary.values()`

{"Element-1", "Element-2", "Element-3", "Element-4", "Element-5"}

This function is opposite to the function `values()`

. As the name suggests, in case you want to view only the **keys** for a dictionary, then you can use the `keys()`

function.

`>>> myDictionary.keys()`

{"Key-1", "Key-2", "Key-3", "Key-4", "Key-5"}

In case you want to display both, **keys** and **values** with a representation, where both are well mapped, then use the `items()`

method.

`>>> myDictionary.items()`

{('Key-1': 'Element-1'), ('Key-2': 'Element-2'), ('Key-3': 'Element-3'), ('Key-4': 'Element-4'), ('Key-5': 'Element-5')}

To check if a particular **key** exists in the dictionary, this function can be used. If the **key** that you are looking for exists then it returns `True`

, otherwise `False`

.

`>>> myDictionary.has_key("Key-2")`

True

`>>> myDictionary.has_key("Key-6")`

False

In case you ever need to compare two dictionaries, `cmp()`

function can be used to do so. It can return 3 possible values, i.e., 1, 0 or -1. If both dictionaries are equal, then 0. If second have greater elements than first, then -1 and 1 for the reverse. It can be used like

```
>>> x = {1: 1, 2:2, 3:3}
>>> y = {1:1, 2:2, 3:3}
>>> cmp(x, y)
```

0

Since both are same, hence the output is `0`

.

Now let's add one an extra element to `x`

.

```
>>> x[4] = 4
>>> cmp(x, y)
```

1

Now that `x`

is having more elements, hence the output is `1`

. Also, if we compare `y`

with `x`

, then

`>>> cmp(y, x)`

-1

The output becomes `-1`

, because `y`

has less elements.