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1. Top results related to what is a dictionary in python

   • What is better in python, a Dictionary or Mysql?

     Top Answer

     Answered Oct 10, 2010 · 5 votes

     Generally speaking, if you want information from a database, ask the database for what you need. MySQL (and other database engines) are designed to retrieve data as efficiently as possible.

     Trying to write your own procedures for retrieving data is trying to outsmart the talented people who have already imbued MySQL with so much data processing power.

     This isn't to say it's never appropriate to load data into Python, but you should be sure that a database query isn't the right way to go first.

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     1/5

   • What is the time complexity of adding new key-value pair to a dictionary in Python?

     Top Answer

     Answered May 12, 2022 · 4 votes

     The update function for dictionaries in Python can be called a few different ways. The first is as a mapping of keys to values followed by optional keyword arguments. The second way is a list of tuples followed by optional keyword arguments. The third is as a series of keyword arguments. We can see these function stubs in builtins.pyi:

     @overloaddef update(self, __m: Mapping[_KT, _VT], **kwargs: _VT) -> None: ...@overloaddef update(self, __m: Iterable[Tuple[_KT, _VT]], **kwargs: _VT) -> None: ...@overloaddef update(self, **kwargs: _VT) -> None: ...

     and this more practical example:

     d_obj = dict()d_obj.update({'a':1},b=2)d_obj.update([('c',3)],d=4)d_obj.update(e=5)print(d_obj)

     For each of these implementations Python will iterate through each argument passed in and check if the key is in the dictionary in constant time. If the key is in the dictionary the function will set the key to its new value. If it is not then the function will add the key to the dictionary and set its value. Since all of these adding and setting operations can be assumed to be done in constant time we can assume each individual item passed in to update() is completed in constant time thus we get O(1 * n) where n is equal to the number of individual key-value pairs passed in to update(). Thus the time complexity of the update function is O(n).

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     2/5

   • What is the proper way of deleting item from a dictionary in "for" loop (Python)?

     Top Answer

     Answered Nov 12, 2011 · 6 votes

     If k is your dictionary, you can do

     k = {x:v for x,v in k.iteritems() if x != 1}-

     For 2.7+ and 3.0

     For anything older, you can do

     k = dict((x,v) for x,v in k.iteritems() if x!=1)

     Check all answers on Stack Overflow

     3/5

   • What is the fastest way to iterate through a dictionary's value in python?

     Top Answer

     Answered Aug 16, 2017 · 5 votes

     As I see it, your way is OK. But if you insist on a different way then you can do:

     from itertools import chainflat_list = list(chain.from_iterable([d.values() for d in some_dict['data']]))for item in flat_list: if item == some_value: # do stuff

     Or, if you only want to check for presence:

     if some_value in flat_list: # do stuff-

     About set, if there are duplicates in the id's values, it will eliminate them. So unless thats fine by you, I wouldn't use it.

     Check all answers on Stack Overflow

     4/5

   • What is the best way to remove a dictionary item by value in python?

     Top Answer

     Answered Oct 18, 2015 · 75 votes

     You can use a simple dict comprehension:

     myDict = {key:val for key, val in myDict.items() if val != 42}-

     As such:

     >>> {key:val for key, val in myDict.items() if val != 42}{8: 14, 1: 'egg'}

     Check all answers on Stack Overflow

     5/5

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2. www.w3schools.com › python › python_dictionariesPython Dictionaries - W3Schools

   www.w3schools.com › python › python_dictionaries

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   A dictionary is a collection which is ordered*, changeable and do not allow duplicates. As of Python version 3.7, dictionaries are ordered. In Python 3.6 and earlier, dictionaries are unordered. Dictionaries are written with curly brackets, and have keys and values:

3. realpython.com › python-dictsDictionaries in Python – Real Python

   realpython.com › python-dicts

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   Python provides another composite data type called a dictionary, which is similar to a list in that it is a collection of objects. Here’s what you’ll learn in this tutorial: You’ll cover the basic characteristics of Python dictionaries and learn how to access and manage dictionary data.

4. www.geeksforgeeks.org › python-dictionaryDictionaries in Python - GeeksforGeeks

   www.geeksforgeeks.org › python-dictionary

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   2 days ago · Dictionaries in Python is a data structure, used to store values in key:value format. This makes it different from lists, tuples, and arrays as in a dictionary each key has an associated value. Note: As of Python version 3.7, dictionaries are ordered and can not contain duplicate keys. How to Create a Dictionary.

5. python.land › python-data-types › dictionariesPython Dictionary: How To Create And Use, With Examples

   python.land › python-data-types › dictionaries

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   Jul 14, 2023 · The Python dictionary is one of the language’s most powerful data types. In other programming languages and computer science in general, dictionaries are also known as associative arrays. They allow you to associate one or more keys to values.

6. www.dataquest.io › blog › python-dictionariesPython Dictionaries: A Comprehensive Tutorial (with 52 Code...

   www.dataquest.io › blog › python-dictionaries

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   Apr 1, 2022 · A Python dictionary is a data structure that allows us to easily write very efficient code. In many other languages, this data structure is called a hash table because its keys are hashable. We'll understand in a bit what this means. A Python dictionary is a collection of key:value pairs.

7. www.freecodecamp.org › news › python-dictionaries-detailed-visual-introductionPython Dictionaries 101: A Detailed Visual Introduction -...

   www.freecodecamp.org › news › python-dictionaries-detailed-visual-introduction

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   Dec 30, 2019 · Dictionaries are built-in data types in Python that associate (map) keys to values, forming key-value pairs. You can access a value with its corresponding key. Keys have to be of an immutable data type. You can access, add, modify, and delete key-value pairs.

8. www.pythontutorial.net › python-basics › python-dictionaryPython Dictionary - Python Tutorial

   www.pythontutorial.net › python-basics › python-dictionary

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   A Python dictionary is a collection of key-value pairs where each key is associated with a value. A value in the key-value pair can be a number , a string , a list , a tuple , or even another dictionary.

9. realpython.com › lessons › dictionary-pythonWhat Is a Dictionary in Python? – Real Python

   realpython.com › lessons › dictionary-python

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   Dictionaries are Python’s implementation of a data structure that is more generally known as an associative array. A dictionary consists of a collection of key-value pairs. Each key-value pair maps the key to its associated value.

10. pynative.com › python-dictionariesDictionaries in Python – PYnative

    pynative.com › python-dictionaries

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    Nov 3, 2022 · Python dictionary represents a mapping between a key and a value. In simple terms, a Python dictionary can store pairs of keys and values. Each key is linked to a specific value. Once stored in a dictionary, you can later obtain the value using just the key.

11. www.tutorialsteacher.com › python › python-dictionaryPython Dictionary (With Examples) - TutorialsTeacher.com

    www.tutorialsteacher.com › python › python-dictionary

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    Python - Dictionary. The dictionary is an unordered collection that contains key:value pairs separated by commas inside curly brackets. Dictionaries are optimized to retrieve values when the key is known. The following declares a dictionary object.