Get All Keys from Dictionary in Python

To get all keys from Dictionary in Python use the keys() method, which returns all keys from the dictionary as a dict_key(). we can also get all keys from a dictionary using various ways in Python. In dictionaries, elements are presented in the form of key:value pairs and all keys are associated with their corresponding values.

Methods to get all keys from the Dictionary:

1. dict.keys() returns the key in the form of dict_keys([comma separated keys])
2. list(dict.keys()) returns the keys as a list.
3. You can use for loop to iterate the dictionary and get the key from each iteration.
4. Use a list comprehension to get all keys from the dictionary.
5. Finally use map() with lambda to get all keys.

1. Quick Examples of Getting All Dictionary Keys

Following are quick examples of getting all dictionary keys in Python.

# Below are the quick examples

# Example 1: Get the keys of dictionary 
# using .keys()
keys = my_dict.keys()

# Example 2: Get the keys of dictionary 
# using .keys() & list()
keys = list(my_dict.keys())

# Example 3: Get the keys using for loop
for key in my_dict.keys():

# Example 4: Get the keys using dictionary comprehension
keys = [key for key in my_dict]

# Example 5: Use map and lambda get the keys of dict
print(list(map(lambda x: x[0], my_dict.items())))

# Example 6:  Using * operator get the keys
print([*my_dict])

# Example 7: Get the specified key based on value
keys = [key for key, value in my_dict.items() if value == 'python']

2. What is Python Dictionary

A Python dictionary is a key-value collection that is unordered, mutable, and does not allow duplicate keys. Each element in the dictionary is in the form of key:value pairs. Dictionary elements should be enclosed with {} and key: value pair separated by commas. The dictionaries are indexed by keys.

Dictionaries are mutable hence, you can be added, deleted, and updated their key:value pairs. keys are an immutable type such as string, numbers(int, float), and tuple. In case, you add duplicates, it will update the existing key with the new value. Let’s create a Python dictionary,

# Create dictionary
my_dict = {'course':'python','fee':4000,'duration':'60days', 'discount':1200}
print(my_dict)

Yields below output.

3. Get All Dictionary Keys using dict.keys()

Using dict.keys() method in Python we can get the all keys from the dictionary in the form view object where the order of keys in a list is the same as the insertion order. Let’s call the keys() function on the above-created dictionary.

# Get the keys from dictionary
keys = my_dict.keys()
print(keys)

If you want to get all the keys in the dictionary in the form of a list use the dict.keys() as an argument to the list(). The list() function takes the dict_keys as an argument and convert it to a list, this will return all keys of the dictionary in the form of a list.

# Get the keys of dictionary as a list 
# using .keys() & list()
keys = list(my_dict.keys())
print(keys)

# Output:
# ['course', 'fee', 'duration', 'discount']

4. Get Dictionary Keys using for Loop

Use for loop to iterate a python dictionary over keys, by default when you use for loop with dict, it returns a key from the dict for each iteration. For example,

# Get the keys using for loop
for key in my_dict.keys():
    print(key)

# Output:
# course
# fee
# duration
# discount

If you wanted to get all keys as a list, use the below example.

# Get the keys using for loop
mylist = []
for key in my_dict.keys():
    mylist.append(key)

print(mylist)

5. Get Dictionary Keys using Comprehension

Alternatively, using comprehension we can get all the keys of the Python dictionary. Let’s use comprehension(a concise way of creating a new list) and get all keys of the dictionary.

# Get the keys as a list using dictionary comprehension
keys = [key for key in my_dict]
print(keys)

# Output
# ['course', 'fee', 'duration', 'discount']

6. Get Keys using Map and lambda

We can also get the dictionary keys using another approach i.e. the combination of a map() function and a lambda function. Let’s use both functions and get our desired output.

# Use map and lambda to get the keys of dict
print(list(map(lambda x: x[0], my_dict.items())))

# Output:
# ['course', 'fee', 'duration', 'discount']

7. Using Unpacking operator(*) & Get the Keys

Using the unpacking operator '*' we can get the all keys from the Python dictionary. This operator works with any iterable object and returns a list. Let’s apply ‘*’ operator on the given dictionary.

# Using * operator get the keys
print([*my_dict])

# Output:
# ['course', 'fee', 'duration', 'discount']

8. Get Key Based on Value in Python

As you know the dictionary keys are associated with their corresponding values. We can get specified keys of a dictionary based on their corresponding value using list comprehension. For example,

# Get the specified key based on value
keys = [key for key, value in my_dict.items() if value == 'python']
print(keys)

# Output:
# ['course']

9. Conclusion

In this Python article, I have explained how to get all keys from the python dictionary using dict.keys() method. Also explained getting keys using map() with lambda, list comprehension, and many other ways.

References

• https://docs.python.org/3/tutorial/datastructures.html#dictionaries