Python Initialize a dictionary with only keys from a list Given a List, the task is to create a dictionary with only keys by using given list as keys. Let’s see the different methods we can do this task.

Dictionary

A dictionary is a collection which is unordered, changeable and indexed. In Python dictionaries are written with curly brackets, and they have keys and values.

• Python: How to Sort a Dictionary by key or Value? Different ways to Iterate / Loop over a Dictionary in Python; Different ways to Remove a key from Dictionary in Python del vs dict.pop Python: 6 Different ways to create Dictionaries; Python Pandas: How to create DataFrame from dictionary? Python: How to get all keys with maximum value.
• Python: How to create a list of all the Values in a dictionary? Python: Filter a dictionary by conditions on keys or values; Python: How to add / append key value pairs in dictionary using dict.update Python: How to find keys by value in dictionary? What is a dictionary in python and why do we need it? Python: How to check if a key.

Example

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Create and print a dictionary:

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Accessing Items

You can access the items of a dictionary by referring to its key name, inside square brackets:

Python List Dictionary Keys

Example

Get the value of the 'model' key:

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There is also a method called get() that will give you the same result:

Example

Get the value of the 'model' key:

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Change Values

You can change the value of a specific item by referring to its key name:

Example

Change the 'year' to 2018:

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Loop Through a Dictionary

You can loop through a dictionary by using a for loop.

When looping through a dictionary, the return value are the keys of the dictionary, but there are methods to return the values as well.

Example

Avast premier 2019 key generator. Print all key names in the dictionary, one by one:

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Print all values in the dictionary, one by one:

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Example

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You can also use the values() function to return values of a dictionary:

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Example

Loop through both keys and values, by using the items() function:

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Check if Key Exists

To determine if a specified key is present in a dictionary use the in keyword:

Example

Check if 'model' is present in the dictionary:

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Dictionary Length

To determine how many items (key-value pairs) a dictionary has, use the len() method.

Example

Print the number of items in the dictionary:

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Adding Items

Adding an item to the dictionary is done by using a new index key and assigning a value to it:

Example

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Removing Items

There are several methods to remove items from a dictionary:

Example

The pop() method removes the item with the specified key name:

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The popitem() method removes the last inserted item (in versions before 3.7, a random item is removed instead):

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The del keyword removes the item with the specified key name:

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Example

The del keyword can also delete the dictionary completely: Generate a putty private key.

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Example

The clear() method empties the dictionary:

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Copy a Dictionary

You cannot copy a dictionary simply by typing dict2 = dict1, because: dict2 will only be a reference to dict1, and changes made in dict1 will automatically also be made in dict2.

There are ways to make a copy, one way is to use the built-in Dictionary method copy().

Example

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Make a copy of a dictionary with the copy() method:

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Another way to make a copy is to use the built-in method dict().

Example

Make a copy of a dictionary with the dict() method:

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Nested Dictionaries

A dictionary can also contain many dictionaries, this is called nested dictionaries.

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Example

Create a dictionary that contain three dictionaries:

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Or, if you want to nest three dictionaries that already exists as dictionaries:

Example

Create three dictionaries, than create one dictionary that will contain the other three dictionaries:

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The dict() Constructor

It is also possible to use the dict() constructor to make a new dictionary:

Example

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Dictionary Methods

Python has a set of built-in methods that you can use on dictionaries.

Method	Description
clear()	Removes all the elements from the dictionary
copy()	Returns a copy of the dictionary
fromkeys()	Returns a dictionary with the specified keys and value
get()	Returns the value of the specified key
items()	Returns a list containing a tuple for each key value pair
keys()	Returns a list containing the dictionary's keys
pop()	Removes the element with the specified key
popitem()	Removes the last inserted key-value pair
setdefault()	Returns the value of the specified key. If the key does not exist: insert the key, with the specified value
update()	Updates the dictionary with the specified key-value pairs
values()	Returns a list of all the values in the dictionary