Frequency of values

Write a Python program to count how often each value appears in a dictionary.

{"a": 10, "b": 20, "c": 25, "d": 10, "e": 30, "f": 20}

{10: 2, 20: 2, 25: 1, 30: 1}

Approach

1. Counter(d.values()).

Solution

from collections import Counterd = {"a": 10, "b": 20, "c": 25, "d": 10, "e": 30, "f": 20}print(dict(Counter(d.values())))

{10: 2, 20: 2, 25: 1, 30: 1}

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Keys with the shortest lists

Write a Python program to find the keys whose list values are the shortest.

{"a": [10, 12], "b": [10], "c": [10, 20, 30, 40], "d": [20]}

['b', 'd']

Approach

1. Find the minimum length, then keep keys with that length.

Solution

d = {"a": [10, 12], "b": [10], "c": [10, 20, 30, 40], "d": [20]}shortest = min(len(v) for v in d.values())print([k for k, v in d.items() if len(v) == shortest])

['b', 'd']

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Keys of the top 2 values

Write a Python program to find the keys of the two largest values.

{"a": 18, "b": 50, "c": 36, "d": 47, "e": 60}

['e', 'b']

Approach

1. Sort keys by value, descending, and take two.

Solution

d = {"a": 18, "b": 50, "c": 36, "d": 47, "e": 60}print(sorted(d, key=d.get, reverse=True)[:2])

['e', 'b']

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Keep even numbers in list values

Write a Python program to keep only even numbers in each list value.

{"a": [11, 4, 6, 15], "b": [3, 8, 12], "c": [5, 3, 10]}

{'a': [4, 6], 'b': [8, 12], 'c': [10]}

Approach

1. Nested comprehensions.

Solution

d = {"a": [11, 4, 6, 15], "b": [3, 8, 12], "c": [5, 3, 10]}print({k: [x for x in v if x % 2 == 0] for k, v in d.items()})

{'a': [4, 6], 'b': [8, 12], 'c': [10]}

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Print the keys

Write a Python program to print the keys of a dictionary, capitalised.

{"pepsi": 50, "sprite": 60, "slice": 55}

Pepsi
Sprite
Slice

Approach

1. Loop over the dict.

Solution

drinks = {"pepsi": 50, "sprite": 60, "slice": 55}for name in drinks:    print(name.title())

Pepsi
Sprite
Slice

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Remove keys whose values contain a substring

Write a Python program to remove entries whose value contains any of the given substrings.

{1: "sqatools is best", 2: "for learning python"}, ["best", "excellent"]

{2: 'for learning python'}

Approach

1. Keep values where no substring is present.

Solution

d = {1: "sqatools is best", 2: "for learning python"}subs = ["best", "excellent"]print({k: v for k, v in d.items() if not any(s in v for s in subs)})

{2: 'for learning python'}

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Remove keys with large values

Write a Python program to remove keys whose values are greater than n.

{"sqa": 3, "tools": 5, "python": 7}, n = 6

{'sqa': 3, 'tools': 5}

Approach

1. Keep v <= n.

Solution

d = {"sqa": 3, "tools": 5, "python": 7}n = 6print({k: v for k, v in d.items() if v <= n})

{'sqa': 3, 'tools': 5}

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Values for keys found in a list

Write a Python program to get the values of dictionary keys that are also in a list.

["sqatools", "is", "best"], {"sqatools": 10}

[10]

Approach

1. Loop over the list and look up keys that exist.

Solution

words = ["sqatools", "is", "best"]d = {"sqatools": 10}print([d[w] for w in words if w in d])

[10]

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Nested dictionary from a list of keys

Write a Python program to nest each item of a dictionary under a key from a list.

{"sqatools": 8, "python": 6}, [1, 2]

{1: {'sqatools': 8}, 2: {'python': 6}}

Approach

1. zip the list with the dict’s items.

Solution

d = {"sqatools": 8, "python": 6}keys = [1, 2]print({k: {name: v} for k, (name, v) in zip(keys, d.items())})

{1: {'sqatools': 8}, 2: {'python': 6}}

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Depth of a nested dictionary

Write a Python program to find the depth of a nested dictionary.

{"a": 1, "b": {"c": {"d": {}}}}

4

Approach

1. Depth is 1 plus the deepest child dictionary’s depth (recursion).

Solution

def depth(d):    if not isinstance(d, dict) or not d:        return 1 if isinstance(d, dict) else 0    return 1 + max(depth(v) for v in d.values()) print(depth({"a": 1, "b": {"c": {"d": {}}}}))

4

Line by line

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