Dictionary

A dictionary maps keys to values allowing efficient retrieval of values from keys

Map

A map is a data structure relating keys to values. For questions about mapping functions use [map-function] instead. For questions about geography, use [maps] instead.



Std large slower

Example

"I definitely wouldn t try introducing a new general-purpose type for use in python based on std map which has worse algorithmic complexity in time for many important operations andâ in at least some implementationsâ leaves some optimisations to the user that dictionary already has"

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Idiomatic way to do list/dict in Cython?

"Std map though is actually implemented in a way that many operations are slower than dictionary as its size gets large"

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Idiomatic way to do list/dict in Cython?

"For suitably large examples of each dictionary overcomes the constant factor by which it s slower than std map and will actually do operations like lookup insertion etc"

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Idiomatic way to do list/dict in Cython?

Function faster entry

Example

"The immutable dictionary implementation is faster but no less pure in usage than the map implementation"

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Can someone point me to examples of multiparadigm (object-functional) programming in F#?

"Then you define the function to convert each entry into a two-element list which will be converted into dictionary automatically using the dictionary function;using map function is faster than just iterating over the list which is the beauty of python"

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Best way to create a dict of the given string in python

"He reason for that is because map is a built-in function and works perfectly better with functions of a built-in function kind chain rule;based on your update you can just use str.replace instead of your function and a generator expression withing dict.fromkeys note that alternatively you could also use for constructing an empty dictionary which is also slightly faster than directly calling the dictionary type"

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How to Maintain Index of List of String After Remove Duplicate?

Key-value pairs comprehension

Example

"So while a dictionary is a type of map maps are a much broader range of possible function;in practice a its usually the mapping function that defines the name so a hashmap is a mapped data structure that uses a hashing algorithm to link the key to the value where as a dictionary doesn t specify how the keys are linked to a value so could be stored via a linked list tree or any other algorithm"

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What is the difference between a map and a dictionary?

"You can use a list comprehension within a dictionary comprehension;since you need both keys and values use dict.items to iterate key-value pairs map works more efficiently with built-ins so you may wish to use or since you have coordinates for tuple values the problem with your logic is python lists do not support vectorised indexing so you need to be explicit the verbose"

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Convert the value of dictionary from list to float

"A map is a key-value pair dictionary not a simple list array as you mentioned in your title;this is my assumption and i might be wrong but something that looks weird to me is this line this one gets via the key i and not by the i th position in the list because a map is not a list"

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Java searching array with for loop doesn't find all results

"Expected output fruit frequency mango 1 apple 2 guava 0 nut 1 the data frame is already there.i just want to map the values with the corresponding element also if my dictionary has more key-value pair than my original dataframe how can i add the keys and corresponding values to dataframe"

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Searching value in a dataframe and then putting corresponding value from dictionary in a new coloumn

"The difference between a map and vector is a like an array while a map is more a dictionary of key value pairs"

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Clojure hashmaps as generalized vectors

"Using this hint we can try to guess that a fixmap must correspond to a dictionary data type in c# since a map is more or less like a dictionary of key-value pairs"

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Trying to get msgpack-cli to give me the same packed byte array as it does in JavaScript

Note series nan

Example

"Note if you pass dictionary map replaces all values from series with nan if it does not match with dictionary s keys i think you have also done the same executing the statement twice"

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Using pandas .map to change values

"Note that the result is a dictionary and not a list containing a single dictionary but it is rather useless to put the result in a list;this works because we first use map to convert the list of dictionaries to a list of counter s"

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Finding min and max elements in the list of dictionary items

Efficient values object

Example

"You could use a list comprehension and fetch the values of interest from each dictionary using operator.itemgetter output or if you prefer with map"

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Formatting key values using map() with a lambda function

"Turning the dictionary values into sets would not gain anything as the conversion would be o n with n being the added size of all values -lists while the above disjoint operation will only iterate each values until it encounters a testx with o 1 lookup;map is possibly more performant compared to a comprehension if you do not have to use lambda if key can be used as the first positional argument in resp s __init__ but certainly not with the lambda"

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What's the most efficient way to perform a multiple match lookup in a python dictionary?

"How about this from a programming perspective this isn t as good a solution as the one that uses an object because an object map dictionary is easier to extend to other values"

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Function that takes a number and returns another number and vice versa

"I could use the map type because checking for membership inside a map dictionary is more efficient than checking for membership in an array"

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Spark DataFrame ArrayType or MapType for checking for value in column

"Different mappings have different ways to hash the input values unless you want to use a sorted dictionary which is more memory efficient but slower"

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Efficient lookup table for unicode code points

Rename columns last

Example

"If ordering of output column should be swapped - first f and then m columns explanation first rename columns by dictionary then set_index by counter series created by cumcount with added 1 and converted to strings reshape by unstack soer second level of multiindex by sort_index flatten multiindex columns by map and join last reset_index for column from index if ordering of output columns is important is possible use double rename of columns"

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Transforming old columns to new columns in Pandas Dataframe

"I think need dataframegroupby.agg with dictionary of columns with lists of functions get multiindex so necessary flattening by map and last rename columns"

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Pandas dataframe groupby function usage

Others

Example

Iiuc if need replace values in some column by dictionary simpliest is remove loop;and if need map where not match get nan

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Python 2.7 replacing all values in a pandas DF

Objects can behave like dictionary because javasript is dynamically typed and there hasn t been a good alternative until now but t really aren t meant to be;the new map functionality is much nicer because it has the expected get set has delete methods you would expect while also accepting any type for the keys instead of just strings

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Map vs Object in JavaScript

The dictionary is not thread safe so if you let one thread read from it while another thread is changing it you will have problems;remember that using lock on the map object doesn t protect the map object in itself it s only using the map reference as an identifier to keep more than one thread at a time to run the code inside the lock

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Thread-safe memoization

Generator expressions are generally preferred to map and using the dictionary constructor is more canonical than dict.fromkeys

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Creating a dictionary that maps ascii characters using map and range

A dictionary that contains fewer emoticons;the fast solution is to simply scrape a more complete dictionary and map the with its corresponding english text translation

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Twitter emoji encoding problems with twitteR and R

Given that keys are enumerated in a random order returning a list with the result doesn t make much sense and dictionary seems more appropriate;note however that for reasons that are not so clear to me map and functional reasoning is sort of considered bad in the python community for example anonymous functions are second-class citizens and second-class citizens got quite close to be completely removed from python 3

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Apply a function on a dict's items

Despite a list with those names and indexes might work i believe a dictionary is semantically better for this case because a dictionary job is to map a key value relation

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From list of str EX: dates into integers - month only

Rather than making a copy of the entire dictionary there is an easier scheme in which you ll just need to make a copy of all the keys in another linked-list;and in the original dictionary in each of the entries just also keep a reference to the linked-list entry corresponding to that key now if you want to iterate the 3 entries at a distance of 5 entries from 4297256046 you just need to do now the reason i mentioned linked-list was so that in case you want to delete any entries from the map you ll be also able to delete the corresponding entry from the linked list in o 1 time

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How to step through a large ordered dictionary in Python 3.7?

I know this question is a bit older but in es2015 there is a new data structure called map that is much more similar to a dictionary that you would use in c#

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C# Dictionary equivalent in JavaScript

If array is long i suggest turning array is long i suggest into a since dictionary is faster has o 1 time complexity vs;o n for array.indexof then or if item.name can be abscent in map

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Sorting list with by a property name according to a fixed set of strings

And use a dictionary in map or replace map is faster for this

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Creating a column in pandas dataframe based off another column

Suddenly a simple dictionary isn t enough you might need a tree of choices attached to each identifier found in the map or a more complex mapping of the identifier with signature data to a scope entry;in many algol like languages look in another scope requires going up the lexical nesting of blocks so each map must have an association with a parent scope

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Implementing the symbol table for a domain specific language using Python

For those who are not familiar with map and indexset check this the logic is that i m iterating over the elements of the given array and each time checking whether the value at that index is not less than value at index + 1 by 1 if it is then i am splitting the array using array slice and adding it in a dictionary having a key which is given by the variable count

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Best way to loop through array and group consecutive numbers in another array SWIFT 4?

And std map shouldn t be compared to dictionary;std map maintains keys in sorted order because it is a balanced tree dictionary solves a different problem

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Idiomatic way to do list/dict in Cython?

Data structure to implement reverse functionality of a dictionary that is more than one key map to a common value using python

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Data structure to implement reverse functionality of a dictionary

C++ std map behaves more like a python defaultdict than dictionary

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Why does += work on std::map keys that don't have values?

safer approach would be to create a private map between a label and myobject using a dictionary instance;a safer approach has the extra overhead of a dictionary but produces more reliable code imho

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Is storing an object reference in a controls Tag property OK

If what you are making is a map from one word to another you might be better off with a dictionary

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Objective C Array of Array of Strings

Map is slightly better because the shared dictionary has around 480 entries instead of around 450 but it s still inconsistent and not all 500 as expected

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Python multiprocessing Pool / Process has inconsistent results

Create a mapper dictionary from df2 using groupby now map the values in df1 using outer key of the dictionary as column and inner dictionary is mapper you get obs gender job 0 1 male blue collar 1 2 male white collar 2 3 female white collar 3 4 male blue collar

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Python pandas: labeling categorical values based on legend dataframe

Benchmarking explanation the reason why s.replace is so slow is that it does much more than simply map a dictionary

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Replace values in a pandas series via dictionary efficiently

Dictionary is an abstract class in java whereas map is an interface;since java does not support multiple inheritances if a class extends dictionary it cannot extend any other class

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What is the difference between a map and a dictionary?

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