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Super Kai (Kazuya Ito)
Super Kai (Kazuya Ito)

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Comprehension in Python (1)

#python #comprehension #list #tuple

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*Memos:

  • My post explains a dictionary(dict) comprehension and generator comprehension.

A comprehension is the concise way to create an iterable. There are a list comprehension, tuple comprehension, set comprehension, dictionary(dict) comprehension and generator comprehension. *A comprehension is an expression.

<List Comprehension>

1D list: 

v = [x**2 for x in range(6)] print(v) # [0, 1, 4, 9, 16, 25]
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*The below is without a list comprehension.

v = [] for x in range(6): v.append(x**2) print(v) # [0, 1, 4, 9, 16, 25]
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2D list: 

sample = [[0, 1, 2], [3, 4, 5]] v = [[y**2 for y in x] for x in sample] print(v) # [[0, 1, 4], [9, 16, 25]]
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*The below is without a list comprehension.

sample = [[0, 1, 2], [3, 4, 5]] v = [] for i, x in enumerate(sample): v.append([]) for y in x: v[i].append(y**2) print(v) # [[0, 1, 4], [9, 16, 25]]
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<Tuple Comprehension>

*tuple() is used for a tuple comprehension because () is already used for a generator comprehension.

1D tuple: 

v = tuple(x**2 for x in range(6)) print(v) # (0, 1, 4, 9, 16, 25)
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*The below is without a tuple comprehension.

v = [] for x in range(6): v.append(x**2) v = tuple(v) print(v) # (0, 1, 4, 9, 16, 25)
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2D tuple: 

sample = [[0, 1, 2], [3, 4, 5]] v = tuple(tuple(y**2 for y in x) for x in sample) print(v) # ((0, 1, 4), (9, 16, 25))
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*The below is without a tuple comprehension.

sample = [[0, 1, 2], [3, 4, 5]] v = [] for i, x in enumerate(sample): v.append([]) for y in x: v[i].append(y**2) v[i] = tuple(v[i]) v = tuple(v) print(v) # [[0, 1, 4], [9, 16, 25]] # ((0, 1, 4), (9, 16, 25))
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<Set Comprehension>

1D set: 

v = {x**2 for x in range(6)} print(v) # {0, 1, 4, 9, 16, 25}
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*The below is without a set comprehension.

v = set() for x in range(6): v.add(x**2) print(v) # {0, 1, 4, 9, 16, 25}
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2D set: 

sample = [[0, 1, 2], [3, 4, 5]] v = {tuple(y**2 for y in x) for x in sample} print(v) # {(9, 16, 25), (0, 1, 4)}
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*The below is without a set comprehension.

sample = [[0, 1, 2], [3, 4, 5]] v = set() for x in sample: def func(x): for y in x: yield y**2 v.add(tuple(func(x))) print(v) # {(9, 16, 25), (0, 1, 4)}
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