Python Dictionary Problems

Python Dictionary Practice Problems.

Split a dictionary into chunks

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Python Practice › Dictionary Programs › Program 92

Split a dictionary into chunks

EasyDictionary Programs · 92 of 94

Write a Python program to split a dictionary into dictionaries of n items.

Input
{"a": 1, "b": 2, "c": 3, "d": 4, "e": 5, "f": 6}, n = 3
Output
[{'a': 1, 'b': 2, 'c': 3}, {'d': 4, 'e': 5, 'f': 6}]

Approach

  1. Slice the list of items in steps of n.

Solution

Python
d = {"a": 1, "b": 2, "c": 3, "d": 4, "e": 5, "f": 6}n = 3items = list(d.items())print([dict(items[i:i + n]) for i in range(0, len(items), n)])
Output
[{'a': 1, 'b': 2, 'c': 3}, {'d': 4, 'e': 5, 'f': 6}]

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#93EasyReverse values and decorate keys#94EasySum of unique values across lists

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Sort by the sum of list values

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Python Practice › Dictionary Programs › Program 91

Sort by the sum of list values

EasyDictionary Programs · 91 of 94

Write a Python program to map each key to the sum of its list and sort by that sum.

Input
{"x": [1, 5, 6], "y": [4, 8, 2], "c": [3, 9]}
Output
{'x': 12, 'c': 12, 'y': 14}

Approach

  1. Sum the lists, then sort by value.

Solution

Python
d = {"x": [1, 5, 6], "y": [4, 8, 2], "c": [3, 9]}sums = {k: sum(v) for k, v in d.items()}print(dict(sorted(sums.items(), key=lambda kv: kv[1])))
Output
{'x': 12, 'c': 12, 'y': 14}

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Sum of unique values across lists

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Python Practice › Dictionary Programs › Program 94

Sum of unique values across lists

EasyDictionary Programs · 94 of 94

Write a Python program to add up the distinct numbers found in all list values.

Input
{"a": [6, 7, 2, 8, 1], "b": [2, 3, 1, 6, 8, 10], "d": [1, 8, 2, 6, 9]}
Output
[1, 2, 3, 6, 7, 8, 9, 10] 46

Approach

  1. Union of all values in a set, then sum.

Solution

Python
d = {"a": [6, 7, 2, 8, 1], "b": [2, 3, 1, 6, 8, 10], "d": [1, 8, 2, 6, 9]}unique = set().union(*d.values())print(sorted(unique), sum(unique))
Output
[1, 2, 3, 6, 7, 8, 9, 10] 46

Line by line

Line 2

set().union(*lists) merges all the lists into one set of distinct numbers.

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#90EasyInvert a dictionary with repeated values#91EasySort by the sum of list values#92EasySplit a dictionary into chunks#93EasyReverse values and decorate keys

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Reverse values and decorate keys

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Python Practice › Dictionary Programs › Program 93

Reverse values and decorate keys

EasyDictionary Programs · 93 of 94

Write a Python program to reverse each string value and put underscores around each key.

Input
{"a": "Python", "b": "Programming", "c": "Learning"}
Output
{'_a_': 'nohtyP', '_b_': 'gnimmargorP', '_c_': 'gninraeL'}

Approach

  1. Dict comprehension with an f-string key and [::-1] value.

Solution

Python
d = {"a": "Python", "b": "Programming", "c": "Learning"}print({f"_{k}_": v[::-1] for k, v in d.items()})
Output
{'_a_': 'nohtyP', '_b_': 'gnimmargorP', '_c_': 'gninraeL'}

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Invert a dictionary with repeated values

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Python Practice › Dictionary Programs › Program 90

Invert a dictionary with repeated values

EasyDictionary Programs · 90 of 94

Write a Python program to invert a dictionary whose values repeat, collecting keys in lists.

Input
{"alex": 1, "bob": 2, "martin": 1, "robert": 2}
Output
{1: ['alex', 'martin'], 2: ['bob', 'robert']}

Approach

  1. setdefault(v, []).append(k).

Solution

Python
d = {"alex": 1, "bob": 2, "martin": 1, "robert": 2}inverted = {}for k, v in d.items():    inverted.setdefault(v, []).append(k)print(inverted)
Output
{1: ['alex', 'martin'], 2: ['bob', 'robert']}

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#91EasySort by the sum of list values#92EasySplit a dictionary into chunks#93EasyReverse values and decorate keys#94EasySum of unique values across lists

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Rename a key

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Python Practice › Dictionary Programs › Program 89

Rename a key

EasyDictionary Programs · 89 of 94

Write a Python program to rename the key “d” to “e”.

Input
{"a": 19, "b": 20, "c": 21, "d": 20}
Output
{'a': 19, 'b': 20, 'c': 21, 'e': 20}

Approach

  1. d["e"] = d.pop("d").

Solution

Python
d = {"a": 19, "b": 20, "c": 21, "d": 20}d["e"] = d.pop("d")print(d)
Output
{'a': 19, 'b': 20, 'c': 21, 'e': 20}

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More dictionary programs

#90EasyInvert a dictionary with repeated values#91EasySort by the sum of list values#92EasySplit a dictionary into chunks#93EasyReverse values and decorate keys

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Delete several keys

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Python Practice › Dictionary Programs › Program 88

Delete several keys

EasyDictionary Programs · 88 of 94

Write a Python program to delete a list of keys from a dictionary.

Input
{"a": 19, "b": 20, "c": 21, "d": 20, "e": 50}, keys ["a", "d", "e"]
Output
{'b': 20, 'c': 21}

Approach

  1. pop(k, None) for each key.

Solution

Python
d = {"a": 19, "b": 20, "c": 21, "d": 20, "e": 50}for k in ["a", "d", "e"]:    d.pop(k, None)print(d)
Output
{'b': 20, 'c': 21}

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More dictionary programs

#89EasyRename a key#90EasyInvert a dictionary with repeated values#91EasySort by the sum of list values#92EasySplit a dictionary into chunks

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Initialise with default values

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Python Practice › Dictionary Programs › Program 87

Initialise with default values

EasyDictionary Programs · 87 of 94

Write a Python program to give every name its own copy of a default settings dictionary.

Input
["Virat", "Rohit"], {"sport": "cricket", "salary": 100000}
Output
{'Virat': {'sport': 'cricket', 'salary': 100000}, 'Rohit': {'sport': 'cricket', 'salary': 120000}}

Approach

  1. Copy the defaults for each name.

Solution

Python
names = ["Virat", "Rohit"]defaults = {"sport": "cricket", "salary": 100000}players = {name: defaults.copy() for name in names}players["Rohit"]["salary"] = 120000print(players)
Output
{'Virat': {'sport': 'cricket', 'salary': 100000}, 'Rohit': {'sport': 'cricket', 'salary': 120000}}

Line by line

Line 3

.copy() gives each player an independent dict, so changing Rohit’s salary does not change Virat’s.

Watch out

dict.fromkeys(names, defaults) would share one dict between all names.

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More dictionary programs

#88EasyDelete several keys#89EasyRename a key#90EasyInvert a dictionary with repeated values#91EasySort by the sum of list values

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List of all values

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Python Practice › Dictionary Programs › Program 86

List of all values

EasyDictionary Programs · 86 of 94

Write a Python program to get a list of all values.

Input
{"sqa": 1, "tools": 2, "is": 2, "best": 4}
Output
[1, 2, 2, 4]

Approach

  1. list(d.values()).

Solution

Python
print(list({"sqa": 1, "tools": 2, "is": 2, "best": 4}.values()))
Output
[1, 2, 2, 4]

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More dictionary programs

#87EasyInitialise with default values#88EasyDelete several keys#89EasyRename a key#90EasyInvert a dictionary with repeated values

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List of all keys

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Python Practice › Dictionary Programs › Program 85

List of all keys

EasyDictionary Programs · 85 of 94

Write a Python program to get a list of all keys.

Input
{"sqa": [1, 2, 5, 6], "tools": [3, 8, 9], "is": [2, 5, 0], "best": [3, 6, 8]}
Output
['sqa', 'tools', 'is', 'best']

Approach

  1. list(d).

Solution

Python
print(list({"sqa": [1, 2, 5, 6], "tools": [3, 8, 9], "is": [2, 5, 0], "best": [3, 6, 8]}))
Output
['sqa', 'tools', 'is', 'best']

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More dictionary programs

#86EasyList of all values#87EasyInitialise with default values#88EasyDelete several keys#89EasyRename a key

← All 94 Dictionary Programs