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2780 votes
22 answers
1.4m views

How to sort a list of dictionaries by a value of the dictionary in Python?

How do I sort a list of dictionaries by a specific key's value? Given: [{'name': 'Homer', 'age': 39}, {'name': 'Bart', 'age': 10}] When sorted by name, it should become: [{'name': 'Bart', 'age': 10}, ...
1744 votes
22 answers
1.3m views

Make a dictionary (dict) from separate lists of keys and values

I want to combine these: keys = ['name', 'age', 'food'] values = ['Monty', 42, 'spam'] into a single dictionary: {'name': 'Monty', 'age': 42, 'food': 'spam'} How can I do this?
Guido's user avatar
  • 47.2k
1298 votes
13 answers
2.0m views

How do I return dictionary keys as a list in Python?

With Python 2.7, I can get dictionary keys, values, or items as a list: >>> newdict = {1:0, 2:0, 3:0} >>> newdict.keys() [1, 2, 3] With Python >= 3.3, I get: >>> newdict....
user avatar
811 votes
13 answers
1.1m views

How do I convert a Map to List in Java?

How do I convert a Map<key,value> to a List<value>? Should I iterate over all map values and insert them into a list?
Javaa's user avatar
  • 8,149
641 votes
7 answers
1.6m views

How can I get list of values from dict?

How can I get a list of the values in a dict in Python? In Java, getting the values of a Map as a List is as easy as doing list = map.values();. I'm wondering if there is a similarly simple way in ...
Muhd's user avatar
  • 24.9k
511 votes
15 answers
555k views

How can I avoid "RuntimeError: dictionary changed size during iteration" error?

Suppose I have a dictionary of lists: d = {'a': [1], 'b': [1, 2], 'c': [], 'd':[]} Now I want to remove key-value pairs where the values are empty lists. I tried this code: for i in d: if not d[i]...
user1530318's user avatar
  • 26.4k
407 votes
6 answers
307k views

Pandas DataFrame to List of Dictionaries

I have the following DataFrame: customer item1 item2 item3 1 apple milk tomato 2 water orange potato 3 juice mango chips which I want ...
Mohamad Ibrahim's user avatar
339 votes
13 answers
229k views

In Python, when to use a Dictionary, List or Set?

When should I use a dictionary, list or set? Are there scenarios that are more suited for each data type?
Blankman's user avatar
  • 263k
317 votes
10 answers
436k views

Getting a list of values from a list of dicts

I have a list of dicts like this: [{'value': 'apple', 'blah': 2}, {'value': 'banana', 'blah': 3} , {'value': 'cars', 'blah': 4}] I want ['apple', 'banana', 'cars'] Whats the best way to do this?...
SuperString's user avatar
299 votes
7 answers
1.2m views

Converting Dictionary to List? [duplicate]

I'm trying to convert a Python dictionary into a Python list, in order to perform some calculations. #My dictionary dict = {} dict['Capital']="London" dict['Food']="Fish&Chips" dict['2012']="...
Federer's user avatar
  • 34.2k
276 votes
19 answers
243k views

Remove duplicate dict in list in Python

I have a list of dicts, and I'd like to remove the dicts with identical key and value pairs. For this list: [{'a': 123}, {'b': 123}, {'a': 123}] I'd like to return this: [{'a': 123}, {'b': 123}] ...
Brenden's user avatar
  • 8,474
267 votes
15 answers
680k views

How to extract all values from a dictionary in Python?

I have a dictionary d = {1:-0.3246, 2:-0.9185, 3:-3985, ...}. How do I extract all of the values of d into a list l?
Naveen C.'s user avatar
  • 3,295
263 votes
13 answers
236k views

How can I convert a dictionary into a list of tuples?

If I have a dictionary like: {'a': 1, 'b': 2, 'c': 3} How can I convert it to this? [('a', 1), ('b', 2), ('c', 3)] And how can I convert it to this? [(1, 'a'), (2, 'b'), (3, 'c')]
mike's user avatar
  • 48k
248 votes
21 answers
715k views

HashMap with multiple values under the same key

Is it possible to implement a HashMap with one key and two values? Just as HashMap<userId, clientID,timeStamp>? If not, is there any other way to implement the storage of multiple values e.g. ...
vidhya's user avatar
  • 2,891
240 votes
12 answers
221k views

How do I merge a list of dicts into a single dict?

How can I turn a list of dicts like [{'a':1}, {'b':2}, {'c':1}, {'d':2}], into a single dict like {'a':1, 'b':2, 'c':1, 'd':2}? Answers here will overwrite keys that match between two of the input ...
killown's user avatar
  • 4,657
233 votes
11 answers
245k views

Create a list with initial capacity in Python

Code like this often happens: l = [] while foo: # baz l.append(bar) # qux This is really slow if you're about to append thousands of elements to your list, as the list will have to be ...
Claudiu's user avatar
  • 227k
231 votes
12 answers
584k views

Convert [key1,val1,key2,val2] to a dict?

Let's say I have a list a in Python whose entries conveniently map to a dictionary. Each even element represents the key to the dictionary, and the following odd element is the value for example, a =...
Mike's user avatar
  • 59.8k
224 votes
8 answers
413k views

How do I get the list of keys in a Dictionary?

I only want the Keys and not the Values of a Dictionary. I haven't been able to get any code to do this yet. Using another array proved to be too much work as I use remove also. How do I get a List of ...
Athiwat Chunlakhan's user avatar
202 votes
8 answers
228k views

Check if value already exists within list of dictionaries in Python?

I've got a Python list of dictionaries as follows: a = [ {'main_color': 'red', 'second_color':'blue'}, {'main_color': 'yellow', 'second_color':'green'}, {'main_color': 'yellow', '...
AP257's user avatar
  • 91.7k
182 votes
5 answers
315k views

C# Convert List<string> to Dictionary<string, string>

This may seem an odd thing to want to do but ignoring that, is there a nice concise way of converting a List<string> to Dictionary<string, string> where each Key Value Pair in the ...
Jonnster's user avatar
  • 3,124
174 votes
7 answers
961k views

How to overcome TypeError: unhashable type: 'list' [duplicate]

I'm trying to take a file that looks like this: AAA x 111 AAB x 111 AAA x 112 AAC x 123 ... And use a dictionary so that the output looks like this {AAA: ['111', '112'], AAB: ['111'], AAC: [123], ...}...
Keenan's user avatar
  • 1,937
170 votes
5 answers
161k views

List of tuples to dictionary [duplicate]

Here's how I'm currently converting a list of tuples to dictionary in Python: l = [('a',1),('b',2)] h = {} [h.update({k:v}) for k,v in l] > [None, None] h > {'a': 1, 'b': 2} Is there a better ...
Sarah Vessels's user avatar
162 votes
11 answers
152k views

What's the difference between [] and {} vs list() and dict()? [closed]

I understand that they are both essentially the same thing. But in terms of creating an empty list or dict, are there any differences?
Noah McIlraith's user avatar
153 votes
3 answers
402k views

Appending to list in Python dictionary [duplicate]

Is there a more elegant way to write this code? What I am doing: I have keys and dates. There can be a number of dates assigned to a key and so I am creating a dictionary of lists of dates to ...
Michael Murphy's user avatar
152 votes
6 answers
130k views

How to find the min/max value of a common key in a list of dicts?

I have a list of dictionaries like so: [{'price': 99, 'barcode': '2342355'}, {'price': 88, 'barcode': '2345566'}] I want to find the min() and max() prices. Now, I can sort this easily enough using a ...
Hank Fay's user avatar
  • 1,774
142 votes
7 answers
144k views

How to convert list of key-value tuples into dictionary?

I have a list that looks like: [('A', 1), ('B', 2), ('C', 3)] I want to turn it into a dictionary that looks like: {'A': 1, 'B': 2, 'C': 3} What's the best way to go about this? EDIT: My list of ...
Fred Wilson's user avatar
  • 1,473
142 votes
5 answers
263k views

Iterating Over Dictionary Key Values Corresponding to List in Python

Working in Python 2.7. I have a dictionary with team names as the keys and the amount of runs scored and allowed for each team as the value list: NL_East = {'Phillies': [645, 469], 'Braves': [599, ...
Burton Guster's user avatar
140 votes
11 answers
172k views

Why can't I use a list as a dict key in python? Exactly what can and cannot be used, and why?

I found that the following are all valid: >>> d = {} >>> d[None] = 'foo' >>> d[(1, 3)] = 'baz' Even a module can be used as a dict key: >>> import sys >>> ...
wim's user avatar
  • 349k
135 votes
14 answers
66k views

List of dicts to/from dict of lists

I want to change back and forth between a dictionary of (equal-length) lists: DL = {'a': [0, 1], 'b': [2, 3]} and a list of dictionaries: LD = [{'a': 0, 'b': 2}, {'a': 1, 'b': 3}]
Adam Greenhall's user avatar
134 votes
4 answers
244k views

python filter list of dictionaries based on key value

I have a list of dictionaries and each dictionary has a key of (let's say) 'type' which can have values of 'type1', 'type2', etc. My goal is to filter out these dictionaries into a list of the same ...
m25's user avatar
  • 1,603
131 votes
7 answers
309k views

Convert dictionary to list collection in C#

I have a problem when trying to convert a dictionary to list. Example if I have a dictionary with template string as key and string as value. Then I wish to convert the dictionary key to list ...
Edy Cu's user avatar
  • 3,292
131 votes
3 answers
221k views

Python: converting a list of dictionaries to json

I have a list of dictionaries, looking some thing like this: list = [{'id': 123, 'data': 'qwerty', 'indices': [1,10]}, {'id': 345, 'data': 'mnbvc', 'indices': [2,11]}] and so on. There may be more ...
Apoorv Ashutosh's user avatar
129 votes
6 answers
175k views

How do I initialize a dictionary of empty lists in Python?

My attempt to programmatically create a dictionary of lists is failing to allow me to individually address dictionary keys. Whenever I create the dictionary of lists and try to append to one key, all ...
Martin Burch's user avatar
  • 2,833
122 votes
6 answers
172k views

How do I combine two lists into a dictionary in Python? [duplicate]

I have two lists of the same length: [1,2,3,4] and [a,b,c,d] I want to create a dictionary where I have {1:a, 2:b, 3:c, 4:d} What's the best way to do this?
SuperString's user avatar
110 votes
9 answers
102k views

How to convert a List into a Map in Dart

I looking for an on-the-shelf way to convert a List into a Map in Dart. In python for example you can do: l= [ ('a',(1,2)), ('b',(2,3)), ('c',(3,4) ) ] d=dict(l) ==> {'a': (1, 2), 'c': (3, 4), 'b'...
Nico's user avatar
  • 1,599
108 votes
13 answers
117k views

In what case would I use a tuple as a dictionary key? [closed]

I was studying the difference between lists and tuples (in Python). An obvious one is that tuples are immutable (the values cannot be changed after initial assignment), while lists are mutable. A ...
Escualo's user avatar
  • 41.4k
108 votes
3 answers
251k views

Appending a dictionary to a list - I see a pointer like behavior

I tried the following in the python interpreter: >>> a = [] >>> b = {1:'one'} >>> a.append(b) >>> a [{1: 'one'}] >>> b[1] = 'ONE' >>> a [{1: 'ONE'}...
neo29's user avatar
  • 1,083
108 votes
2 answers
395k views

Python, TypeError: unhashable type: 'list'

I'm receiving the following error in my program. The traceback: Traceback (most recent call last): File "C:\Python33\Archive\PythonGrafos\Alpha.py", line 126, in <module> menugrafos() ...
Rex's user avatar
  • 1,211
105 votes
5 answers
134k views

One liner: creating a dictionary from list with indices as keys

I want to create a dictionary out of a given list, in just one line. The keys of the dictionary will be indices, and values will be the elements of the list. Something like this: a = [51,27,13,56] ...
Sarfaraz Nawaz's user avatar
105 votes
4 answers
477k views

Convert list into a dictionary [duplicate]

l = ["a", "b", "c", "d", "e"] I want to convert this list to a dictionary like: d = {"a": "b", "c": "d", "e": ""} So basically, the evens will be keys whereas the odds will be values. I know that I ...
Shaokan's user avatar
  • 7,526
103 votes
5 answers
132k views

Python - sum values in dictionary

I have got pretty simple list: example_list = [ {'points': 400, 'gold': 2480}, {'points': 100, 'gold': 610}, {'points': 100, 'gold': 620}, {'points': 100, 'gold': 620} ] How can I ...
Mateusz Jagiełło's user avatar
99 votes
8 answers
102k views

Python: get a dict from a list based on something inside the dict

I need to be able to find an item in a list (an item in this case being a dict) based on some value inside that dict. The structure of the list I need to process looks like this: [ { '...
johneth's user avatar
  • 2,868
94 votes
10 answers
193k views

How to get dictionary values as a generic list, when each entry's value is a list

I just want get a list from Dictionary values but it's not so simple as it appears ! here the code : Dictionary<string, List<MyType>> myDico = GetDictionary(); List<MyType> items = ...
Florian's user avatar
  • 4,627
90 votes
10 answers
118k views

Remove dictionary from list

If I have a list of dictionaries, say: [{'id': 1, 'name': 'paul'}, {'id': 2, 'name': 'john'}] and I would like to remove the dictionary with id of 2 (or name 'john'), what is the most efficient way ...
john a macdonald's user avatar
89 votes
9 answers
94k views

Mapping dictionary value to list

Given the following dictionary: dct = {'a':3, 'b':3,'c':5,'d':3} How can I apply these values to a list such as: lst = ['c', 'd', 'a', 'b', 'd'] in order to get something like: lstval = [5, 3, 3, ...
ulrich's user avatar
  • 3,567
86 votes
3 answers
225k views

Python Array with String Indices

Is it possible to use strings as indices in an array in python? For example: myArray = [] myArray["john"] = "johns value" myArray["jeff"] = "jeffs value" print myArray["john"]
Petey B's user avatar
  • 11.5k
86 votes
9 answers
160k views

How do I serialize a Python dictionary into a string, and then back to a dictionary?

How do I serialize a Python dictionary into a string, and then back to a dictionary? The dictionary will have lists and other dictionaries inside it.
TIMEX's user avatar
  • 265k
82 votes
11 answers
167k views

how to convert list of dict to dict

How to convert list of dict to dict. Below is the list of dict data = [{'name': 'John Doe', 'age': 37, 'sex': 'M'}, {'name': 'Lisa Simpson', 'age': 17, 'sex': 'F'}, {'name': 'Bill ...
sush's user avatar
  • 6,007
79 votes
1 answer
21k views

Is there a class like Dictionary<> in C#, but for just keys, no values?

I guess another way to phrase this would be "Is there a class like List<> in C#, but optimized for checking whether a particular value is present?" I'm sure for a small set of values List<>...
Chuck Wilbur's user avatar
  • 2,570
76 votes
8 answers
240k views

How can I create an array/list of dictionaries in python?

I have a dictionary as follows: {'A':0,'C':0,'G':0,'T':0} I want to create an array with many dictionaries in it, as follows: [{'A':0,'C':0,'G':0,'T':0},{'A':0,'C':0,'G':0,'T':0},{'A':0,'C':0,'G':0,...
Adrian Randall's user avatar

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