Python 学习笔记(二)
Aug 25, 2016
通过将索引指定为 -1,可让 Python 返回最后一个列表元素:
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3bicycles = ['trek', 'cannondale', 'redline', 'specialized']
print(bicycles[-1]) # specialized
print(bicycles[-2]) # redline-2、-3 以此类推。
从列表中删除某个位置的元素:
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5motorcycles = ['honda', 'yamaha', 'suzuki']
print(motorcycles) # ['honda', 'yamaha', 'suzuki']
del motorcycles[0]
print(motorcycles) # ['yamaha', 'suzuki']方法 pop() 可删除列表末尾的元素,也可弹出列表位置处的元素:
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6motorcycles = ['honda', 'yamaha', 'suzuki']
print(motorcycles) # ['honda', 'yamaha', 'suzuki']
poped_motorcycle = motorcycles.pop()
print(motorcycles) # ['honda', 'yamaha']
print(poped_motorcycle) # suzuki1
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6motorcycles = ['honda', 'yamaha', 'suzuki']
print(motorcycles) # ['honda', 'yamaha', 'suzuki']
poped_motorcycle = motorcycles.pop(1)
print(motorcycles) # ['honda', 'suzuki']
print(poped_motorcycle) # yamaha根据值删除元素:
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5motorcycles = ['honda', 'yamaha', 'suzuki', 'ducati']
print(motorcycles) # ['honda', 'yamaha', 'suzuki', 'ducati']
motorcycles.remove('ducati')
print(motorcycles) # ['honda', 'yamaha', 'suzuki']方法
remove()
只删除第一个出现的指定值,如果要删除的值可能在列表中出现多次,则需要使用循环来判断是否删除了所有这样的值。使用 方法
sort()
对列表进行永久性排序,使用 函数sorted()
对列表进行临时排序:1
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3cars = ['bmw', 'audi', 'toyota', 'subaru']
cars.sort()
print(cars) # ['audi', 'bmw', 'subaru', 'toyota']1
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3cars = ['bmw', 'audi', 'toyota', 'subaru']
print(sorted(cars)) # ['audi', 'bmw', 'subaru', 'toyota']
print(cars) # ['bmw', 'audi', 'toyota', 'subaru']倒着打印列表:
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3cars = ['bmw', 'audi', 'toyota', 'subaru']
cars.reverse()
print(cars)永久性修改列表元素的排列顺序,但可再次调用
reverse()
可随时恢复到原来的排列顺序。确定列表的长度:
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2cars = ['bmw', 'audi', 'toyota', 'subaru']
print(len(cars)) # 4