Creating a new dictionary in Python

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I want to build a dictionary in Python. However, all the examples that I see are instantiating a dictionary from a list, etc . ..

How do I create a new empty dictionary in Python?

Call dict with no parameters

new_dict = dict()

or simply write

new_dict = {}

How to Create an Empty Dictionary in Python, Call dict with no parameters new_dict = dict(). or simply write new_dict = {}. To create your dictionary variable in Python, you have to use the curly brackets({}) to place the elements. Each element contains keys and its matched element. The elements are indexed and start from index zero(0). You have to place dictionary variable in comma separation.

You can do this

x = {}
x['a'] = 1

Python Dictionary(Dict): Update, Cmp, Len, Sort, Copy, Items, str , In this tutorial, you'll learn everything about Python dictionaries; how they are Dictionary comprehension is an elegant and concise way to create a new  How to Create and Use a Dictionary in Python. 1 Open a Python Shell window. You see the familiar Python prompt. 2 Type Colors = {“Sam”: “Blue”, “Amy”: “Red”, “Sarah”: “Yellow”} and press Enter. 3 Type Colors and press Enter. 4 Type Colors[“Sarah”] and press Enter. 5 Type Colors.keys( ) and press

Knowing how to write a preset dictionary is useful to know as well:

cmap =  {'US':'USA','GB':'Great Britain'}

# Explicitly:
# -----------
def cxlate(country):
    try:
        ret = cmap[country]
    except KeyError:
        ret = '?'
    return ret

present = 'US' # this one is in the dict
missing = 'RU' # this one is not

print cxlate(present) # == USA
print cxlate(missing) # == ?

# or, much more simply as suggested below:

print cmap.get(present,'?') # == USA
print cmap.get(missing,'?') # == ?

# with country codes, you might prefer to return the original on failure:

print cmap.get(present,present) # == USA
print cmap.get(missing,missing) # == RU

Python : How to add / append key value pairs in dictionary using dict , into two elements Keys and Values. Keys will be a single element. This post may contain affiliate links. Please read disclosure for more info. Dictionaries are the unordered way of mapping and storing objects. It uses the key-value pair. It enclosed by the curly braces {}. Let’s start how to create a Dictionary in Python. Existing data in the dictionary. Print the dictionary.

>>> dict(a=2,b=4)
{'a': 2, 'b': 4}

Will add the value in the python dictionary.

How do I add data to a dictionary in python? Python Dictionary Dictionaries are optimized to retrieve values when the key is known. Creating a dictionary is as simple as placing items inside curly braces {} separated by comma,. An item has a key and a corresponding value that is expressed as a pair (key: value).

d = dict()

or

d = {}

or

import types
d = types.DictType.__new__(types.DictType, (), {})

, if any key already exists then it will update its value. Add New Key Value Pair In Dictionary With Python If you want to add a newly chosen key and value to the Dictionary. You have to use the new key and assign the new value to it. Check the below example to assign a new value with the new key.

Create a new dictionary. # In order to construct a dictionary you can start with an empty one. >>> mydict={} # This will create a dictionary, which  Python Dictionary Comprehension Dictionary comprehension is a method for transforming one dictionary into another dictionary. During this transformation, items within the original dictionary can be conditionally included in the new dictionary and each item can be transformed as needed.

In Python dictionaries are written with curly brackets, and they have keys and values. It is also possible to use the dict() constructor to make a new dictionary:​  How to Create an Empty Dictionary in Python. In this article, we show how to create an empty dictionary in Python. A dictionary in Python is really an associative array or hash table that is composed of key-value pairs. So if you have a dictionary called itemprices, one key may be "T-shirt" with a value of 24.95, another key may be "Brief" with a value of 14.95, a

You can start by creating an empty dictionary, which is specified by empty curly braces. Then you can add new keys and values one at a time: >>> >>> person  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. You can access the items of a dictionary by referring to its key name, inside square brackets: There is also a method called get () that will give you the same result:

Comments
  • Is there any difference between dict() and {}? Or do people just prefer one over the other?
  • @ Matt Apparently CPython 2.7 dict() is slower (6 times slower?), See: doughellmann.com/2012/11/… In any case I am starting to prefer the constructor syntax anyways since I find it easier to type and move code between dicts and function calls.
  • I confirm it's 3 times faster to use { } than dict() in python 3.x
  • Yeah, I get about 4 times faster in python 3.6 for {} over dict() and 5 times for [] over list().
  • In the vast majority of cases, it doesn't matter if it takes six times longer, since that's still an unnoticeably small amount of time.
  • +1 for next logical question of how to add a new element to it
  • Good point! But I think the bit with cxlate makes your answer seem too complicates. I'd just keep the initialization part. (cxlate itself is too complicated. You could just return cmap.get(country, '?').)
  • Consider using docs.python.org/2/library/… instead of writing a translate function or using .get() everywhere.
  • Perhaps I would, except that the documentation is absolutely opaque to me -- it's terrible. I have no idea what they're telling me to do, or why I should do it. And .get() seems to do exactly the right thing -- plus it's extremely flexible. I'm sure its a lack of understanding on my part. With that in mind, my questions are: why bother? What is saved here, easier here, faster here, etc.? Benefit is exactly what?
  • Unrelated, but you should explicitly catch the KeyError instead of a bare except (which would catch things such as KeyboardInterrupt and SystemExit).
  • Arnav, yes of course you're right. Edited accordingly. Thank you!
  • What is the difference between types.DictType.__new__(types.DictType, (), {}) and just {}
  • For anyone reading this: the last "solution" is a bit of a joke - you can use it (in python 2.x at least - won't work in py3k), but no one in it's own mind would ever want to do so ;-)
  • the question states that the dictionary should be a new empty instance