Python dictionary access by index

Python Dictionary: How to Get a Key by Index — Tips and Tricks

Learn how to get a dictionary key by index in Python with tips and tricks. Explore different functions, best practices, and common issues with dictionaries.

• Dictionaries in Python
• Python dictionary keys() function
• Ways to get a dictionary key by index
• The Python get() function
• The Python dict.item() function
• Best practices and additional tips
• Other code examples for accessing a dictionary key by index in Python
• Conclusion
• How to access the keys from a Python dictionary using index?
• How to index keys in Python?
• How to find the value of a dictionary variable in Python?
• How to find the value of a known key in Python?

As a programmer, you must have come across dictionaries in Python — an essential part of the language that is used to store key-value pairs. However, unlike lists or tuples, dictionaries do not have an inherent order, making it difficult to get a dictionary key by index. In this blog post, we will explore how to get a dictionary key by index in Python and discuss some tips and tricks to work with dictionaries more efficiently.

Dictionaries in Python

Dictionaries in Python are unordered sets of key-value pairs. They are defined using curly braces (<>) and separated by a colon(:). For example:

In the above example, “apple”, “banana”, and “orange” are keys, and 2, 3, and 5 are their respective values.

Unlike lists or tuples, dictionaries do not have an index order, which means that it’s not possible to get a dictionary key by index. However, there are ways to achieve this.

Python dictionary keys() function

The Python dictionary keys() function can be used to get all the keys in a dictionary. However, this function does not return the keys in any specific order, and therefore it does not solve the problem of getting a dictionary key by index. The syntax to use this function is:

Ways to get a dictionary key by index

There are two ways to get a dictionary key by index in Python. The first way is to convert the dictionary keys to a list and then access the index of the list. The second way is to use itertools.islice to index the dictionary keys.

Converting dictionary keys to a list

To convert the dictionary keys to a list, you can use the list() function. The syntax to use this function is:

Once you have a list of keys, you can access the index of the list to get the corresponding key. For example, to get the key at index 1:

Using itertools.islice

itertools.islice is a function in the Python standard library that can be used to slice an iterable. In this case, we can use it to slice the dictionary keys. The syntax to use this function is:

import itertoolsnext(itertools.islice(my_dict.keys(), index, index+1)) 

In the above example, index is the index of the key you want to get.

The Python get() function

The Python get() function can be used to get the value of a known key in a dictionary. However, this function does not directly solve the problem of getting a dictionary key by index. The syntax to use this function is:

In the above example, key is the key you want to get the value for.

The Python dict.item() function

The Python dict.item() function can be used to fetch the key from a value. However, this function does not directly solve the problem of getting a dictionary key by index. The syntax to use this function is:

[item for item in my_dict.items() if item[1] == value][0][0] 

In the above example, value is the value you want to get the key for.

Best practices and additional tips

When working with dictionaries in python , it’s important to be aware of their advantages and disadvantages. One common issue with dictionaries is accidentally overwriting existing keys. To avoid this, you can use the defaultdict class in Python, which initializes a dictionary with default values. The counter class in Python can be used to count the frequency of elements in a dictionary.

Another best practice for iterating over a dictionary in python is to use the items() function, which returns a list of (key, value) pairs. For example:

for key, value in my_dict.items(): print(key, value) 

Other code examples for accessing a dictionary key by index in Python

In Python , get dictionary elements by index in python code sample

value_at_index = list(dic.values())[index]

In Python case in point, dictionary access key by index code example

my_dict = index = 1 #element index we want key = list(my_dict.keys())[index] # finding key name using element index print(my_dictPython dictionary access by index)

mydict = print(list(mydict.keys())[list(mydict.values()).index(16)]) # Prints george

In Python , in particular, how to retrieve dictionary values in python by index code sample

a_dictionary = keys_list = list(a_dictionary) key = keys_list[0] print(key)

In Python , dict get value by index code example

dic = <> value_at_index = dic.ElementAt(index)

Conclusion

In conclusion, dictionaries in Python do not have an index order, making it difficult to get a dictionary key by index. However, by converting the dictionary keys to a list or using itertools.islice , it’s possible to achieve this. Additionally, the Python get() and dict.item() functions can be used to get the value of a known key or fetch the key from a value. By following best practices and being aware of common issues with dictionaries , working with them can be made more efficient and effective.

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Python dictionary access by index

Last updated: Feb 21, 2023
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# Table of Contents

# Get the index of a Key in a Dictionary and access the key

To get the index of a key in a dictionary:

1. Use the list() class to convert the dictionary to a list of keys.
2. Use the list.index() method to get the position of the key in the dictionary.
3. The list.index() method will return the index of the specified key.

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my_dict =  'id': 1, 'name': 'Bobbyhadz', 'age': 30, > index = None if 'name' in my_dict: index = list(my_dict).index('name') print(index) # 👉️ 1 key = list(my_dict)[1] print(key) # 👉️ name value = list(my_dict.values())[1] print(value) # 👉️ Bobbyhadz 

Once we find the index of the key in a dictionary, we have to convert the dictionary to a list to access it.

We used the list() class to convert the dictionary to a list of keys.

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my_dict =  'id': 1, 'name': 'Bobbyhadz', 'age': 30, > print(list(my_dict)) # 👉️ ['id', 'name', 'age'] print(list(my_dict.keys())) # 👉️ ['id', 'name', 'age'] 

We could have also used the dict.keys() method to be more explicit.

The dict.keys method returns a new view of the dictionary’s keys.

The last step is to use the list.index() method to get the position of the key in the dictionary.

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my_dict =  'id': 1, 'name': 'Bobbyhadz', 'age': 30, > index = None if 'name' in my_dict: index = list(my_dict).index('name') print(index) # 👉️ 1 

The list.index() method returns the index of the first item whose value is equal to the provided argument.

The method raises a ValueError if there is no such item in the list.

We used an if statement to check if the key exists in the dictionary, so the list.index() method will never throw a ValueError .

# Accessing Dictionary keys or values by Index

You can use the index to get the key and value at the specific position.

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my_dict =  'id': 1, 'name': 'Bobbyhadz', 'age': 30, > index = None if 'name' in my_dict: index = list(my_dict).index('name') print(index) # 👉️ 1 key = list(my_dict)[index] print(key) # 👉️ name value = list(my_dict.values())[index] print(value) # 👉️ Bobbyhadz 

To get the key at the specific position, we just have to convert the dictionary to a list of keys and access the list at the index.

To get the value, we convert the dict.values() view to a list and access it at the index.

The dict.values method returns a new view of the dictionary’s values.

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my_dict = 'id': 1, 'name': 'bobbyhadz'> print(my_dict.values()) # 👉️ dict_values([1, 'bobbyhadz']) 

# Accessing dictionary values by key

Note that unless you have a good reason to access the keys and values in the dictionary using an index, using bracket notation is much more performant.

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my_dict =  'id': 1, 'name': 'Bobbyhadz', 'age': 30, 'address':  'country': 'Chile' >, 'tasks': ['dev', 'test'] > print(my_dict['name']) # 👉️ Bobbyhadz print(my_dict['address']) # 👉️ print(my_dict['address']['country']) # 👉️ Chile print(my_dict['tasks'][0]) # 👉️ dev 

You can specify a key between the square brackets to access the corresponding value.

# Accessing Dictionary Items by Index

You can also use the dict.items() method to get a dictionary key-value pair by index.

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my_dict =  'id': 1, 'name': 'Bobbyhadz', 'age': 30, > index = 1 key, value = list(my_dict.items())[index] print(key) # 👉️ name print(value) # 👉️ Bobbyhadz 

The dict.items method returns a new view of the dictionary’s items ((key, value) pairs).

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my_dict =  'id': 1, 'name': 'Bobbyhadz', 'age': 30, > # 👇️ dict_items([('id', 1), ('name', 'Bobbyhadz'), ('age', 30)]) print(my_dict.items()) 

The dict_items object is not subscriptable (cannot be accessed at an index), so we used the list() class to convert it to a list.

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my_dict =  'id': 1, 'name': 'Bobbyhadz', 'age': 30, > index = 1 key, value = list(my_dict.items())[index] print(key) # 👉️ name print(value) # 👉️ Bobbyhadz 

Python indexes are zero-based, so the first item in a list has an index of 0 , and the last item has an index of -1 or len(a_list) — 1 .

# Getting the index of multiple keys in a dictionary

If you need to get the position of multiple keys in the dictionary, use a for loop.

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my_dict =  'id': 1, 'name': 'Bobbyhadz', 'age': 30, > keys = ['name', 'age'] for key in keys: if key in my_dict: # name - 1 # age - 2 print(f'key> - list(my_dict).index(key)>') 

On each iteration, we check if the key is contained in the dictionary and print the corresponding index.

# Accessing Dictionary keys or values by Index with enumerate()

You can also use the enumerate() function to access dictionary keys or values by index.

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my_dict =  'id': 1, 'name': 'Bobbyhadz', 'age': 30, > index = 1 key = next( key for idx, key in enumerate(my_dict) if idx == index ) print(key) # 👉️ name # ------------------------------------------------------ value = next( value for idx, value in enumerate(my_dict.values()) if idx == index ) print(value) # 👉️ Bobbyhadz 

The enumerate function takes an iterable and returns an enumerate object containing tuples where the first element is the index and the second is the corresponding item.

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my_dict =  'id': 1, 'name': 'Bobbyhadz', 'age': 30, > for index, key in enumerate(my_dict): # 0 id # 1 name # 2 age print(index, key) 

On each iteration, we check if the current index is equal to the specified index and return the corresponding key or value.

# Getting all dictionary keys that have a specific value

If you need to get all dictionary keys that have a specific value, use a list comprehension.

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my_dict =  'id': 1, 'name': 'Bobbyhadz', 'age': 30, 'salary': 30, > keys = [key for key, value in my_dict.items() if value == 30] print(keys) # 👉️ ['age', 'salary'] 

List comprehensions are used to perform some operation for every element or select a subset of elements that meet a condition.

On each iteration, we check if the current value is equal to 30 and return the result.

The keys list only stores the keys of the items that have a value of 30 .

# Using the OrderedDict class instead

As of Python 3.7, the standard dict class is guaranteed to preserve the insertion order of keys.

You can check your version of python by issuing the python —version command.

If you use an older version (than 3.7), use the OrderedDict class instead.

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from collections import OrderedDict my_dict = OrderedDict( [('id', 1), ('name', 'Bobbyhadz'), ('age', 30)] ) key = list(my_dict)[1] print(key) # 👉️ name value = list(my_dict.values())[1] print(value) # 👉️ Bobbyhadz index = None if 'name' in my_dict: index = list(my_dict).index('name') print(index) # 👉️ 1 

The list() class can also be used to convert the keys of an OrderedDict to a list.

Note that using the OrderedDict class is only necessary if you use a version older than Python 3.7.

Otherwise, use the native dict class as it preserves insertion order.

# Additional Resources

You can learn more about the related topics by checking out the following tutorials:

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