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Python Articles
Page 816 of 855
What do the =+ and += do in Python?
The += operator is syntactic sugar for object.__iadd__() function. From the python docs:These methods are called to implement the augmented arithmetic assignments (+=, -=, *=, @=, /=, //=, %=, **=, =, &=, ^=, |=). These methods should attempt to do the operation in-place (modifying self) and return the result (which could be, but does not have to be, self).ExampleSo when you do something like −a = 5 b = 10 a += b print(a)OutputThis will give the output −15a is being modified in place here. You can read more about such operators on https://docs.python.org/3/reference/datamodel.html#object.__iadd__.The =+ operator is the same as ...
Read MoreHow to find the average of non-zero values in a Python dictionary?
You can do this by iterating over the dictionary and filtering out zero values first. Then take the sum of the filtered values. Finally, divide by the number of these filtered values. examplemy_dict = {"foo": 100, "bar": 0, "baz": 200} filtered_vals = [v for _, v in my_dict.items() if v != 0] average = sum(filtered_vals) / len(filtered_vals) print(average)OutputThis will give the output −150.0You can also use reduce but for a simple task such as this, it is an overkill. And it is also much less readable than using a list comprehension.
Read MoreHow to access nested Python dictionary items via a list of keys?
The easiest and most readable way to access nested properties in a Python dict is to use for loop and loop over each item while getting the next value, until the end. exampledef getFromDict(dataDict, mapList): for k in mapList: dataDict = dataDict[k] return dataDict a = { 'foo': 45,'bar': { 'baz': 100,'tru': "Hello" } } print(getFromDict(a, ["bar", "baz"]))OutputThis will give the output −100
Read MoreFinding The Biggest Key In A Python Dictionary?
If you have a dict with string-integer mappings, you can use the max method on the dictionary's item pairs to get the largest value. exampled = { 'foo': 100, 'bar': 25, 'baz': 360 } print(max(k for k, v in d.items()))OutputThis will give the output −foofoo is largest in alphabetical order.
Read MoreFilling Bookcase Shelves in Python
Suppose we have a sequence of books − Here the i-th book has thickness books[i][0] and height books[i][1]. If we want to place these books in order onto bookshelves that have total width shelf_width. If we choose some of the books to place on this shelf (such that the sum of their thickness is = 0 and temp – books[j, 0] >= 0, docurr_height := max of books[j, 1], curr_heightdp[i] := min of dp[i], curr_height + (dp[j - 1] if j – 1 >= 0, otherwise 0)temp := temp – books[j, 0]decrease j by 1return last element of dpLet us ...
Read MoreDo you think Python Dictionary is really Mutable?
Yes, Python Dictionary is mutable. Changing references to keys doesn't lead to the creation of new dictionaries. Rather it updates the current dictionary in place. examplea = {'foo': 1, 'bar': 12} b = a b['foo'] = 20 print(a) print(b)OutputThis will give the output −{'foo': 20, 'bar': 12} {'foo': 20, 'bar': 12}
Read MoreHow can I convert Python dictionary to JavaScript hash table?
Python and javascript both have different representations for a dictionary. So you need an intermediate representation in order to pass data between them. The most commonly used intermediate representation is JSON, which is a simple lightweight data-interchange format.The dumps function converts the dict to a string. exampleimport json my_dict = { 'foo': 42, 'bar': { 'baz': "Hello", 'poo': 124.2 } } my_json = json.dumps(my_dict) print(my_json)OutputThis will give the output −'{"foo": 42, "bar": {"baz": "Hello", "poo": 124.2}}'exampleThe load's function converts the string back to a dict. import json my_str = '{"foo": 42, "bar": {"baz": "Hello", "poo": 124.2}}' my_dict ...
Read MorePath With Maximum Minimum Value in Python
Suppose we have a matrix A of integers with R rows and C columns, we have to find the maximum score of a path starting from [0, 0] and ending at [R-1, C-1]. Here the scoring technique will be the minimum value in that path. For example, the value of the path 8 → 4 → 5 → 9 is 4. A path moves some number of times from one visited cell to any neighboring unvisited cell in one of the 4 cardinal directions (north, east, west, south).For example, if the grid is like −545126746The orange cells will be the ...
Read MoreHow to check for redundant combinations in a Python dictionary?
There will never be redundant combinations in a Python dictionary because it is a hashmap. This means that each key will have exactly one associated value with it. This value can be a list or another dict though. So if you try to add a duplicate key likeExamplea = {'foo': 42, 'bar': 55} a['foo'] = 100 print(a)OutputThis will give the output{'foo': 100, 'bar': 55}If you really want multiple values for a single key, then you should probably use a list to be associated with the key and add values to that list.
Read MoreSmallest Subsequence of Distinct Characters in Python
Suppose we have a text, we have to find the lexicographically smallest subsequence of text that contains all the distinct characters of text exactly once. So if the input is like “cdadabcc”, then the output will be “adbc”.To solve this, we will follow these steps −Define a stack st, two maps last_o and considered, they are initially blankfor i in range length of text – 1 down to 0if text[i] is not present in last_o −last_o[text[i]] := iconsidered[text[i]] := falsei := 0while i < length of textif stack has no elementspush text[i] into stackconsidered[text[i]] := trueincrease i by 1otherwise stack ...
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