Get first key-value pair from a Python Dictionary

In this article, we will discuss different ways to fetch first key-value pair from a dictionary. Then we will also learn about a way to get first N key-value pairs from a python dictionary.

Table of Contents

Get first key-value pair of dictionary in python using iter() & next()

The items() function of dictionary returns an iterable sequence of all key-value pairs of the dictionary. We can create an iterator object of this iterable sequence of key-value pairs using iter() function. The iter() function accepts a sequence as argument and returns an iterator. Then by calling the next() function with this iterator object, we can get the first element of this sequence i.e. first key-value pair of the dictionary. For example,

# A dictionary of string and integers
word_freq = {
    'Hello' : 56,
    "at"    : 23,
    'test'  : 43,
    'This'  : 78,
    'Why'   : 11
}

# Get first key-value pair of the dictionary
first_pair = next(iter((word_freq.items())) )

print('First Key Value Pair of Dictionary:')
print(first_pair)

print('First Key: ', first_pair[0])
print('First Value: ', first_pair[1])

Output:

First Key Value Pair of Dictionary:
('Hello', 56)
First Key:  Hello
First Value:  56

We fetched the iterable sequence of key-vaue pairs of dictionary and then selected the first key-vaue pair from the dictionary.

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Get first key-value pair of dictionary using list

As items() function of the dictionary class returns an iterable sequence of all key-value pairs of the dictionary. We can cast that sequence to a list and then select first item from that list. That will be our first key-value pair from the dictionary. For example,

# A dictionary of string and integers
word_freq = {
    'Hello' : 56,
    "at"    : 23,
    'test'  : 43,
    'This'  : 78,
    'Why'   : 11
}

# Get first key-value pair of the dictionary
first_pair = list(word_freq.items())[0]

print('First Key Value Pair of Dictionary:')
print(first_pair)

print('Key: ', first_pair[0])
print('Value: ', first_pair[1])

Output:

First Key Value Pair of Dictionary:
('Hello', 56)
Key:  Hello
Value:  56

We created a list of all key-value pairs from the dictionary. Then selected the first item from list, which is the first key-value pair of the dictionary.

Related Stuff:

Get first N key-value pair of dictionary in python using list & slicing

Create a list of all key-value pairs from the dictionary, as we did in the previous example. Then select first N entries from the list by slicing ( list[start:end] ) i.e. to select first N entries, slice it using list[:N]. Let’s see an example, where we will select first 3 key-value pairs from a dictionary,

# A dictionary of string and integers
word_freq = {
    'Hello' : 56,
    "at"    : 23,
    'test'  : 43,
    'This'  : 78,
    'Why'   : 11
}

n = 3
# Get first 3 key-value pairs of the dictionary
first_n_pairs = list(word_freq.items())[:n]

print('First 3 Key Value Pairs of Dictionary:')

for key,value in first_n_pairs:
    print(key, '::', value)

Output:

First 3 Key Value Pairs of Dictionary:
Hello :: 56
at :: 23
test :: 43

We created a list of all key-value pairs from the dictionary. Then selected first 3 items from that list, which are the first 3 key-value pairs of the dictionary.

Get first N key-value pair of dictionary in python using itertools

In Python, the items() function of dictionary returns an iterable sequence of all key-value pairs of the dictionary. Then using the itertools.islice(iterable, stop), we can slice first N entries from the sequence. Let’s see an example, where we will select first 3 key-value pairs from a dictionary,

import itertools

# A dictionary of string and integers
word_freq = {
    'Hello' : 56,
    "at"    : 23,
    'test'  : 43,
    'This'  : 78,
    'Why'   : 11
}

n = 3
# Get first 3 key-value pairs of the dictionary
first_n_pairs = itertools.islice(word_freq.items(), n)

print('First 3 Key Value Pairs of Dictionary:')

for key,value in first_n_pairs:
    print(key, '::', value)

Output:

First 3 Key Value Pairs of Dictionary:
Hello :: 56
at :: 23
test :: 43

The islice() function returns an iterator, whose next() method returns selected values from an iterable. To select the first 3 entries from sequence returned by items(), we passed the sequence and 3 as arguments in the islice() function. Therefore it returned an iterator to a sliced sequence containing first 3 key-value pairs of the original dictionary.

Conclusion:

Here, we learned about different ways to select firs key-value pair from a python dictionary. Then we also looked at ways to select first N pairs from the dictionary.

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