Python Dictionary Problems

Python Dictionary Practice Problems.

Length of each value

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Python Practice › Dictionary Programs › Program 64

Length of each value

EasyDictionary Programs · 64 of 94

Write a Python program to map each string value to its length.

Input
{1: "sqa", 2: "tools", 3: "python"}
Output
{'sqa': 3, 'tools': 5, 'python': 6}

Approach

  1. {v: len(v) for v in d.values()}.

Solution

Python
d = {1: "sqa", 2: "tools", 3: "python"}print({v: len(v) for v in d.values()})
Output
{'sqa': 3, 'tools': 5, 'python': 6}

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Values for one key from a list of dicts

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Python Practice › Dictionary Programs › Program 63

Values for one key from a list of dicts

EasyDictionary Programs · 63 of 94

Write a Python program to extract the values for a key from a list of dictionaries.

Input
[{"t20": 50, "odi": 70}, {"t20": 40, "odi": 10}, {"t20": 30, "odi": 0}, {"t20": 45, "odi": 65}], key "odi"
Output
[70, 10, 0, 65]

Approach

  1. [d["odi"] for d in data].

Solution

Python
data = [{"t20": 50, "odi": 70}, {"t20": 40, "odi": 10}, {"t20": 30, "odi": 0}, {"t20": 45, "odi": 65}]print([d["odi"] for d in data])
Output
[70, 10, 0, 65]

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Update list values

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Python Practice › Dictionary Programs › Program 62

Update list values

EasyDictionary Programs · 62 of 94

Write a Python program to add 10 to every number in the first list and subtract 25 from the second.

Input
{"virat": [50, 30], "rohit": [40, 10]}
Output
{'virat': [60, 40], 'rohit': [15, -15]}

Approach

  1. Rebuild each list with a comprehension.

Solution

Python
d = {"virat": [50, 30], "rohit": [40, 10]}d["virat"] = [x + 10 for x in d["virat"]]d["rohit"] = [x - 25 for x in d["rohit"]]print(d)
Output
{'virat': [60, 40], 'rohit': [15, -15]}

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#63EasyValues for one key from a list of dicts#64EasyLength of each value#65MediumDepth of a nested dictionary#66EasyNested dictionary from a list of keys

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Empty every list value

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Python Practice › Dictionary Programs › Program 61

Empty every list value

EasyDictionary Programs · 61 of 94

Write a Python program to clear the list values in a dictionary.

Input
{"virat": [50, 30], "rohit": [40, 10]}
Output
{'virat': [], 'rohit': []}

Approach

  1. clear() each list in place.

Solution

Python
d = {"virat": [50, 30], "rohit": [40, 10]}for v in d.values():    v.clear()print(d)
Output
{'virat': [], 'rohit': []}

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#62EasyUpdate list values#63EasyValues for one key from a list of dicts#64EasyLength of each value#65MediumDepth of a nested dictionary

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Convert string values to numbers

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Python Practice › Dictionary Programs › Program 60

Convert string values to numbers

EasyDictionary Programs · 60 of 94

Write a Python program to convert the string values of a dictionary to int or float.

Input
{"a": "30", "b": "20", "c": "10"}, {"a": "3.33", "b": "20.50", "c": "12.5"}
Output
{'a': 30, 'b': 20, 'c': 10}
{'a': 3.33, 'b': 20.5, 'c': 12.5}

Approach

  1. Use int when the text has no decimal point, otherwise float.

Solution

Python
def to_number(text):    return float(text) if "." in text else int(text) for d in [{"a": "30", "b": "20", "c": "10"}, {"a": "3.33", "b": "20.50", "c": "12.5"}]:    print({k: to_number(v) for k, v in d.items()})
Output
{'a': 30, 'b': 20, 'c': 10}
{'a': 3.33, 'b': 20.5, 'c': 12.5}

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#61EasyEmpty every list value#62EasyUpdate list values#63EasyValues for one key from a list of dicts#64EasyLength of each value

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Remove a dictionary from a list

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Python Practice › Dictionary Programs › Program 59

Remove a dictionary from a list

EasyDictionary Programs · 59 of 94

Write a Python program to remove the 4th dictionary from a list.

Input
[{"t20": 50, "odi": 70}, {"t20": 40, "odi": 10}, {"t20": 30, "odi": 0}, {"t20": 45, "odi": 65}]
Output
[{'t20': 50, 'odi': 70}, {'t20': 40, 'odi': 10}, {'t20': 30, 'odi': 0}]

Approach

  1. pop(3).

Solution

Python
data = [{"t20": 50, "odi": 70}, {"t20": 40, "odi": 10}, {"t20": 30, "odi": 0}, {"t20": 45, "odi": 65}]data.pop(3)print(data)
Output
[{'t20': 50, 'odi': 70}, {'t20': 40, 'odi': 10}, {'t20': 30, 'odi': 0}]

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Group key-value pairs into lists

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Python Practice › Dictionary Programs › Program 57

Group key-value pairs into lists

EasyDictionary Programs · 57 of 94

Write a Python program to group a sequence of (key, value) pairs into a dictionary of lists.

Input
[("virat", 50), ("rohit", 40), ("virat", 30), ("rohit", 10)]
Output
{'virat': [50, 30], 'rohit': [40, 10]}

Approach

  1. defaultdict(list).

Solution

Python
from collections import defaultdict pairs = [("virat", 50), ("rohit", 40), ("virat", 30), ("rohit", 10)]groups = defaultdict(list)for k, v in pairs:    groups[k].append(v)print(dict(groups))
Output
{'virat': [50, 30], 'rohit': [40, 10]}
Note

A dict literal cannot hold the same key twice, so the input is a list of pairs.

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More dictionary programs

#58EasyDict of lists to list of dicts#59EasyRemove a dictionary from a list#60EasyConvert string values to numbers#61EasyEmpty every list value

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Are all values the same?

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Python Practice › Dictionary Programs › Program 56

Are all values the same?

EasyDictionary Programs · 56 of 94

Write a Python program to check whether all values in a dictionary are the same.

Input
{"virat": 50, "rohit": 50, "rahul": 50, "hardik": 50}
Output
True

Approach

  1. A set of the values has one item when they are all equal.

Solution

Python
d = {"virat": 50, "rohit": 50, "rahul": 50, "hardik": 50}print(len(set(d.values())) == 1)
Output
True

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#57EasyGroup key-value pairs into lists#58EasyDict of lists to list of dicts#59EasyRemove a dictionary from a list#60EasyConvert string values to numbers

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Matrix rows to a dictionary

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Python Practice › Dictionary Programs › Program 55

Matrix rows to a dictionary

EasyDictionary Programs · 55 of 94

Write a Python program to convert a matrix into a dictionary keyed by row number.

Input
[[1, 2, 3], [4, 5, 6]]
Output
{1: [1, 2, 3], 2: [4, 5, 6]}

Approach

  1. enumerate(matrix, start=1).

Solution

Python
matrix = [[1, 2, 3], [4, 5, 6]]print(dict(enumerate(matrix, start=1)))
Output
{1: [1, 2, 3], 2: [4, 5, 6]}

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#56EasyAre all values the same?#57EasyGroup key-value pairs into lists#58EasyDict of lists to list of dicts#59EasyRemove a dictionary from a list

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String to a dictionary

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Python Practice › Dictionary Programs › Program 54

String to a dictionary

EasyDictionary Programs · 54 of 94

Write a Python program to convert “key=value; key=value” text into a dictionary.

Input
"Apr=April; Mar=March"
Output
{'Apr': 'April', 'Mar': 'March'}

Approach

  1. Split on “;”, then split each part on “=” and strip spaces.

Solution

Python
text = "Apr=April; Mar=March"d = dict(part.strip().split("=") for part in text.split(";"))print(d)
Output
{'Apr': 'April', 'Mar': 'March'}

Line by line

Line 2

strip() removes the space after each semicolon, so the second key is “Mar”, not ” Mar”.

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More dictionary programs

#55EasyMatrix rows to a dictionary#56EasyAre all values the same?#57EasyGroup key-value pairs into lists#58EasyDict of lists to list of dicts

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