Python Practice Problems

Python practice problems help beginners to become experts in a python programming language with a small amount of practice effort.

Values for keys found in a list

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Python Practice › Dictionary Programs › Program 67

Values for keys found in a list

EasyDictionary Programs · 67 of 94

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

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

Approach

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

Solution

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

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More dictionary programs

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Nested dictionary from a list of keys

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Python Practice › Dictionary Programs › Program 66

Nested dictionary from a list of keys

EasyDictionary Programs · 66 of 94

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

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

Approach

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

Solution

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

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More dictionary programs

#67EasyValues for keys found in a list#68EasyRemove keys with large values#69EasyRemove keys whose values contain a substring#70EasyPrint the keys

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Depth of a nested dictionary

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Python Practice › Dictionary Programs › Program 65

Depth of a nested dictionary

MediumDictionary Programs · 65 of 94

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

Input
{"a": 1, "b": {"c": {"d": {}}}}
Output
4

Approach

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

Solution

Python
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": {}}}}))
Output
4

Line by line

Lines 2-3

An empty dict has depth 1; a non-dict value adds nothing.

Line 4

Each level adds 1 to the deepest value below it.

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More dictionary programs

#66EasyNested dictionary from a list of keys#67EasyValues for keys found in a list#68EasyRemove keys with large values#69EasyRemove keys whose values contain a substring

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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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More dictionary programs

#65MediumDepth of a nested dictionary#66EasyNested dictionary from a list of keys#67EasyValues for keys found in a list#68EasyRemove keys with large values

← All 94 Dictionary Programs

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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More dictionary programs

#64EasyLength of each value#65MediumDepth of a nested dictionary#66EasyNested dictionary from a list of keys#67EasyValues for keys found in a list

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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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More dictionary programs

#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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More dictionary programs

#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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More dictionary programs

#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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More dictionary programs

#60EasyConvert string values to numbers#61EasyEmpty every list value#62EasyUpdate list values#63EasyValues for one key from a list of dicts

← All 94 Dictionary Programs

Dict of lists to list of dicts

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Python Practice › Dictionary Programs › Program 58

Dict of lists to list of dicts

EasyDictionary Programs · 58 of 94

Write a Python program to split a dictionary of lists into a list of dictionaries.

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

Approach

  1. zip(*d.values()) gives one row per position.

Solution

Python
d = {"t20": [50, 40, 30, 45], "odi": [70, 10, 0, 65]}print([dict(zip(d, row)) for row in zip(*d.values())])
Output
[{'t20': 50, 'odi': 70}, {'t20': 40, 'odi': 10}, {'t20': 30, 'odi': 0}, {'t20': 45, 'odi': 65}]

Learn the concept

New to this topic? Read the lesson, then come back.

More dictionary programs

#59EasyRemove a dictionary from a list#60EasyConvert string values to numbers#61EasyEmpty every list value#62EasyUpdate list values

← All 94 Dictionary Programs