1、列表推导
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numbers = [i for i in range(10) if i % 2 == 0]
print(numbers)
seq = ["one", "two", "three"]
for i, element in enumerate(seq):
print(i, element)
def treatment(pos, element):
return ('%d: %s' % (pos, element))
print ([treatment(i, element) for i, element in enumerate(seq)])
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enumerate(sequence, [start=0])
Return an enumerate object.
sequence must be a sequence, an iterator, or some other object which supports iteration.
The next() method of the iterator returned by enumerate() returns a tuple containing a count (from start which defaults to 0) and the corresponding value obtained from iterating over iterable.
enumerate() is useful for obtaining an indexed series: (0, seq[0]), (1, seq[1]), (2,seq[2]), ....
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2、迭代器
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class MyIterator(object):
def __init__(self, step):
self.step = step
def __next__(self): # 3.0之后一般采用该样式
if self.step == 0:
raise StopIteration
self.step -= 1
return self.step
def __iter__(self):
return self
for i in MyIterator(5):
print(i)
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3、生成器
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def fibonacci():
a, b = 0, 1
while True:
yield b
a, b = b, a + b
fib = fibonacci()
print([next(fib) for i in range(10)]) # >=python 3.0
print(fib.__next__() for i in range(10)]) # >=python 3.0
print(fib.next() for i in range(10)]) # <python 3.0
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