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Python List Practice Problems
Write a Python program to check whether an element exists in a list.
[3, 9, 27], check 9 and 4
9 exists 4 does not exist
in.numbers = [3, 9, 27]for x in [9, 4]: print(x, "exists" if x in numbers else "does not exist")9 exists 4 does not exist
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Write a Python program to replace the first and last numbers of a list with “SQA” and “Tools”.
[12, 32, 33, 5, 4, 7]
['SQA', 32, 33, 5, 4, 'Tools']
numbers = [12, 32, 33, 5, 4, 7]numbers[0] = "SQA"numbers[-1] = "Tools"print(numbers)['SQA', 32, 33, 5, 4, 'Tools']
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Write a Python program to convert a string into a list of words and a list of characters.
"learn python"
['learn', 'python'] ['l', 'e', 'a', 'r', 'n', ' ', 'p', 'y', 't', 'h', 'o', 'n']
split() for words, list() for characters.text = "learn python"print(text.split())print(list(text))['learn', 'python'] ['l', 'e', 'a', 'r', 'n', ' ', 'p', 'y', 't', 'h', 'o', 'n']
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Write a Python program to get the numbers that appear exactly once in a list.
[1, 2, 2, 3, 4, 4, 5]
[1, 3, 5] [1, 2, 3, 4, 5]
Counter and keep counts of 1.from collections import Counter numbers = [1, 2, 2, 3, 4, 4, 5]counts = Counter(numbers)print([n for n in numbers if counts[n] == 1])print(list(dict.fromkeys(numbers)))[1, 3, 5] [1, 2, 3, 4, 5]
Values that occur only once.
Every distinct value (duplicates removed), for comparison.
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Write a Python program to get all keys and all values from a list of single-item dictionaries.
[{"a": 12}, {"b": 34}, {"c": 23}, {"d": 11}, {"e": 15}]['a', 'b', 'c', 'd', 'e'] [12, 34, 23, 11, 15]
data = [{"a": 12}, {"b": 34}, {"c": 23}, {"d": 11}, {"e": 15}]keys = [k for d in data for k in d]values = [v for d in data for v in d.values()]print(keys)print(values)['a', 'b', 'c', 'd', 'e'] [12, 34, 23, 11, 15]
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Write a Python program to combine items at the same position of two lists into sublists.
[3, 5, 7, 8, 9], [1, 4, 3, 6, 2]
[[3, 1], [5, 4], [7, 3], [8, 6], [9, 2]]
zip pairs items; convert each pair to a list.a = [3, 5, 7, 8, 9]b = [1, 4, 3, 6, 2]print([[x, y] for x, y in zip(a, b)])[[3, 1], [5, 4], [7, 3], [8, 6], [9, 2]]
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Write a Python program to reverse each string in a list.
["Sqa", "Tools", "Online", "Learning", "Platform"]
['aqS', 'slooT', 'enilnO', 'gninraeL', 'mroftalP']
[::-1] to every item.words = ["Sqa", "Tools", "Online", "Learning", "Platform"]print([w[::-1] for w in words])['aqS', 'slooT', 'enilnO', 'gninraeL', 'mroftalP']
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Write a Python program to get the items in the first list that are not in the second.
[1, 2, 3, 4, 5], [2, 4, 6]
[1, 3, 5] [1, 3, 5, 6]
a = [1, 2, 3, 4, 5]b = [2, 4, 6]print([x for x in a if x not in b])print(sorted(set(a) ^ set(b)))[1, 3, 5] [1, 3, 5, 6]
Items only in a, in their original order.
The symmetric difference gives items in exactly one of the lists.
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Write a Python program to merge all elements of a list into one string using a special character.
["sqa", "tools", 2026, "python"], separator "#"
sqa#tools#2026#python
items = ["sqa", "tools", 2026, "python"]print("#".join(str(x) for x in items))sqa#tools#2026#python
join only accepts strings, so the number is converted first.
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Write a Python program to find the second smallest number in a list.
[10, 4, 32, 4, 18]
10
numbers = [10, 4, 32, 4, 18]print(sorted(set(numbers))[1])10
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