python中的set學習
阿新 • • 發佈:2019-02-13
集合是獨立不同個體的無序集合。示例如下:
animals = {'cat', 'dog'}
print 'cat' in animals # Check if an element is in a set; prints "True"
print 'fish' in animals # prints "False"
animals.add('fish') # Add an element to a set
print 'fish' in animals # Prints "True"
print len(animals) # Number of elements in a set; prints "3"
animals.add('cat') # Adding an element that is already in the set does nothing
print len(animals) # Prints "3"
animals.remove('cat') # Remove an element from a set
print len(animals) # Prints "2"
和前面一樣,要知道更詳細的,檢視文件。
迴圈Loops:在集合中迴圈的語法和在列表中一樣,但是集合是無序的,所以你在訪問集合的元素的時候,不能做關於順序的假設。
animals = {'cat', 'dog', 'fish'}
for idx, animal in enumerate(animals):
print '#%d: %s' % (idx + 1, animal)
# Prints "#1: fish", "#2: dog", "#3: cat"
集合推導Set comprehensions:和字典推導一樣,可以很方便地構建集合:
from math import sqrt
nums = {int(sqrt(x)) for x in range(30)}
print nums # Prints "set([0, 1, 2, 3, 4, 5])"