dictionary

Get the last element in a dictionary?

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What do you mean by Last? Do you mean Last value added? The Dictionary<TKey,TValue> class is an unordered collection. Adding and removing items can change what is considered to be the first and last element. Hence there is no way to get the Last element added. There is an ordered dictionary class available in the … Read more

In Python, How can I get the next and previous key:value of a particular key in a dictionary?

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Edit: OP now states that they are using OrderedDicts but the use case still requires this sort of approach. Since dicts are not ordered you cannot directly do this. From your example, you are trying to reference the item like you would use a linked list. A quick solution would be instead to extract the … Read more

Python: How to turn a dictionary of Dataframes into one big dataframe with column names being the key of the previous dict?

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You can try first set_index of all dataframes in comprehension and then use concat with remove last level of multiindex in columns: print d {‘17012016’: Fruit Price 0 Orange 7 1 Apple 8 2 Pear 9, ‘16012016’: Fruit Price 0 Orange 4 1 Apple 5 2 Pear 6, ‘15012016’: Fruit Price 0 Orange 1 1 … Read more

How do I extract all the values of a specific key from a list of dictionaries?

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If you just need to iterate over the values once, use the generator expression: generator = ( item[‘value’] for item in test_data ) … for i in generator: do_something(i) Another (esoteric) option might be to use map with itemgetter – it could be slightly faster than the generator expression, or not, depending on circumstances: from … Read more

Python: Create Dictionary from Text/File that’s in Dictionary Format

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You can use the eval built-in. For example, this would work if each dictionary entry is on a different line: dicts_from_file = [] with open(‘myfile.txt’,’r’) as inf: for line in inf: dicts_from_file.append(eval(line)) # dicts_from_file now contains the dictionaries created from the text file Alternatively, if the file is just one big dictionary (even on multiple … Read more

Partial match for the key of a std::map

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You can’t efficiently search for substring, but you can for prefix: #include <iostream> #include <map> #include <string> #include <algorithm> using namespace std; typedef map<string, string> TStrStrMap; typedef pair<string, string> TStrStrPair; TStrStrMap::const_iterator FindPrefix(const TStrStrMap& map, const string& search_for) { TStrStrMap::const_iterator i = map.lower_bound(search_for); if (i != map.end()) { const string& key = i->first; if (key.compare(0, search_for.size(), … Read more

Dictionary access speed comparison with integer key against string key

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CPython’s dict implementation is in fact optimized for string key lookups. There are two different functions, lookdict and lookdict_string (lookdict_unicode in Python 3), which can be used to perform lookups. Python will use the string-optimized version until a search for non-string data, after which the more general function is used. You can look at the … Read more

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