Python基础（二）之数据类型和运算（4）—— 列表
列表
Python 有几个 复合数据类型，用于表示其它的值。最通用的是 list (列表) ，它可以写作中括号之间的一列逗号分隔的值。列表的元素不必是同一类型:
>>> squares = [1, 4, 9, 16, 25] >>> squares [1, 4, 9, 16, 25]
索引：
names = ['Alex',"Tenglan",'Eric'] >>> names[0] 'Alex' >>> names[2] 'Eric' >>> names[-1] 'Eric' >>> names[-2] #还可以倒着取 'Tenglan'
切片：
print(name_list[1:4])#取下标1至下标4之间的值，包括1，不包括4
print(name_list[1:-1])#取下标1至下标-1的值，不包括-1（-1为最右边的值） print(name_list[1:])#从1开始取直到最后一个，不能写-1，只能这么写 print(name_list[1:len(name_list)])#同上 print(name_list[0:3])#从头开始取，取3个值 print(name_list[:3])#如果是从头开始取，0可以忽略，跟上句效果一样 print(name_list[0::2])#后面的2表示每隔一个元素，取一个 print(name_list[::2])#效果同上 print(name_list[-3:-1])#从右边数第3个到最后一个，不包括最后第一个
print(name_list[-3:])#从右边数第3个到最后一个
所有的切片操作都会返回一个包含请求的元素的新列表。这意味着下面的切片操作返回列表一个新的（浅）拷贝副本:
print(name_list[:])
修改：
>>> names ['Alex', 'Tenglan', '强行从Eric前面插入', 'Eric', 'Rain', '从eric后面插入试试新姿势', 'Tom', 'Amy', '我是新来的'] >>> names[2] = "该换人了" >>> names ['Alex', 'Tenglan', '该换人了', 'Eric', 'Rain', '从eric后面插入试试新姿势', 'Tom', 'Amy', '我是新来的']
也可以对切片赋值，此操作可以改变列表的尺寸，或清空它:
>>> letters = ['a', 'b', 'c', 'd', 'e', 'f', 'g'] >>> letters ['a', 'b', 'c', 'd', 'e', 'f', 'g'] >>> # replace some values >>> letters[2:5] = ['C', 'D', 'E'] >>> letters ['a', 'b', 'C', 'D', 'E', 'f', 'g'] >>> # now remove them >>> letters[2:5] = [] >>> letters ['a', 'b', 'f', 'g'] >>> # clear the list by replacing all the elements with an empty list >>> letters[:] = [] >>> letters []
追加：
>>> names ['Alex', 'Tenglan', 'Eric', 'Rain', 'Tom', 'Amy'] >>> names.append("我是新来的") >>> names ['Alex', 'Tenglan', 'Eric', 'Rain', 'Tom', 'Amy', '我是新来的']
扩展：
>>> names ['Alex', 'Tenglan', 'Rain', 'Tom', 'Amy'] >>> b = [1,2,3] >>> names.extend(b) >>> names ['Alex', 'Tenglan', 'Rain', 'Tom', 'Amy', 1, 2, 3]
列表也支持连接这样的操作:
>>> squares + [36, 49, 64, 81, 100]
[1, 4, 9, 16, 25, 36, 49, 64, 81, 100]
插入：
>>> names ['Alex', 'Tenglan', 'Eric', 'Rain', 'Tom', 'Amy', '我是新来的'] >>> names.insert(2,"强行从Eric前面插入") >>> names ['Alex', 'Tenglan', '强行从Eric前面插入', 'Eric', 'Rain', 'Tom', 'Amy', '我是新来的'] >>> names.insert(5,"从eric后面插入试试新姿势") >>> names ['Alex', 'Tenglan', '强行从Eric前面插入', 'Eric', 'Rain', '从eric后面插入试试新姿势', 'Tom', 'Amy', '我是新来的']
删除：
>>> del names[2] >>> names ['Alex', 'Tenglan', 'Eric', 'Rain', '从eric后面插入试试新姿势', 'Tom', 'Amy', '我是新来的'] >>> del names[4] >>> names ['Alex', 'Tenglan', 'Eric', 'Rain', 'Tom', 'Amy', '我是新来的'] >>> >>> names.remove("Eric") #删除指定元素，只能删一个 >>> names ['Alex', 'Tenglan', 'Rain', 'Tom', 'Amy', '我是新来的'] >>> names.pop() #删除列表最后一个值 '我是新来的' >>> names ['Alex', 'Tenglan', 'Rain', 'Tom', 'Amy']
拷贝：
>>> names ['Alex', 'Tenglan', 'Rain', 'Tom', 'Amy', 1, 2, 3] >>> name_copy = names.copy() >>> name_copy ['Alex', 'Tenglan', 'Rain', 'Tom', 'Amy', 1, 2, 3]
此处的copy只能浅拷贝，即只能拷贝一层，例如：
>>> text = ['a','b','c','d',['A','B','C'],'e','f']>>> text_copy = text.copy() >>> text_copy ['a', 'b', 'c', 'd', ['A', 'B', 'C'], 'e', 'f'] >>> text[4][1] = 'ZZZ' >>> text ['a', 'b', 'c', 'd', ['A', 'ZZZ', 'C'], 'e', 'f'] >>> text_copy #并没有修改text_copy的内容，但是却被更改。证明这个copy 是浅拷贝 ['a', 'b', 'c', 'd', ['A', 'ZZZ', 'C'], 'e', 'f']
在列表嵌套列表的存储中，实际存的是子列表的指针，浅拷贝拷贝的也是相应子列表指针，所以更改子列表元素原列表和复制列表都会改变。
>>> text_copy[4][0] = 'Yang' >>> text ['a', 'b', 'c', 'd', ['Yang', 'ZZZ', 'C'], 'e', 'f'] >>> text_copy ['a', 'b', 'c', 'd', ['Yang', 'ZZZ', 'C'], 'e', 'f']
深层拷贝：
import copy #拷贝模块
text = ['a','b','c','d',['A','B','C'],'e','f'] print(" text=",text) text_copy = copy.deepcopy(text) #深层拷贝 print("text_copy=",text_copy) text[4][1] = "ZZZ" print("Chang text: text=",text) print("Chang text: text_copy=",text_copy) text_copy[4][0] = "Yang" print("Chang text_copy: text=",text) print("Chang text_copy: text_copy=",text_copy) 输出： text= ['a', 'b', 'c', 'd', ['A', 'B', 'C'], 'e', 'f'] text_copy= ['a', 'b', 'c', 'd', ['A', 'B', 'C'], 'e', 'f'] Chang text: text= ['a', 'b', 'c', 'd', ['A', 'ZZZ', 'C'], 'e', 'f'] Chang text: text_copy= ['a', 'b', 'c', 'd', ['A', 'B', 'C'], 'e', 'f'] Chang text_copy: text= ['a', 'b', 'c', 'd', ['A', 'ZZZ', 'C'], 'e', 'f'] Chang text_copy: text_copy= ['a', 'b', 'c', 'd', ['Yang', 'B', 'C'], 'e', 'f']
深拷贝是完全拷贝，子列表也重新保存。
浅拷贝三种：
p1 = copy.copy(person) p2 = person[:] p3 = list(person)
统计：
>>> names ['Alex', 'Tenglan', 'Amy', 'Tom', 'Amy', 1, 2, 3] >>> names.count("Amy") 2
排序&翻转：
>>> names ['Alex', 'Tenglan', 'Amy', 'Tom', 'Amy', 1, 2, 3] >>> names.sort() #排序 Traceback (most recent call last): File "<stdin>", line 1, in <module> TypeError: unorderable types: int() < str() #3.0里不同数据类型不能放在一起排序了，擦 >>> names[-3] = '1' >>> names[-2] = '2' >>> names[-1] = '3' >>> names ['Alex', 'Amy', 'Amy', 'Tenglan', 'Tom', '1', '2', '3'] >>> names.sort() >>> names ['1', '2', '3', 'Alex', 'Amy', 'Amy', 'Tenglan', 'Tom'] >>> names.reverse() #反转 >>> names ['Tom', 'Tenglan', 'Amy', 'Amy', 'Alex', '3', '2', '1']
获取下标：
>>> names ['Tom', 'Tenglan', 'Amy', 'Amy', 'Alex', '3', '2', '1'] >>> names.index("Amy") 2 #只返回找到的第一个下标
class list(object): """ list() -> new empty list list(iterable) -> new list initialized from iterable's items """ def append(self, p_object): # real signature unknown; restored from __doc__ """ L.append(object) -- append object to end """ pass def count(self, value): # real signature unknown; restored from __doc__ """ L.count(value) -> integer -- return number of occurrences of value """ return 0 def extend(self, iterable): # real signature unknown; restored from __doc__ """ L.extend(iterable) -- extend list by appending elements from the iterable """ pass def index(self, value, start=None, stop=None): # real signature unknown; restored from __doc__ """ L.index(value, [start, [stop]]) -> integer -- return first index of value. Raises ValueError if the value is not present. """ return 0 def insert(self, index, p_object): # real signature unknown; restored from __doc__ """ L.insert(index, object) -- insert object before index """ pass def pop(self, index=None): # real signature unknown; restored from __doc__ """ L.pop([index]) -> item -- remove and return item at index (default last). Raises IndexError if list is empty or index is out of range. """ pass def remove(self, value): # real signature unknown; restored from __doc__ """ L.remove(value) -- remove first occurrence of value. Raises ValueError if the value is not present. """ pass def reverse(self): # real signature unknown; restored from __doc__ """ L.reverse() -- reverse *IN PLACE* """ pass def sort(self, cmp=None, key=None, reverse=False): # real signature unknown; restored from __doc__ """ L.sort(cmp=None, key=None, reverse=False) -- stable sort *IN PLACE*; cmp(x, y) -> -1, 0, 1 """ pass def __add__(self, y): # real signature unknown; restored from __doc__ """ x.__add__(y) <==> x+y """ pass def __contains__(self, y): # real signature unknown; restored from __doc__ """ x.__contains__(y) <==> y in x """ pass def __delitem__(self, y): # real signature unknown; restored from __doc__ """ x.__delitem__(y) <==> del x[y] """ pass def __delslice__(self, i, j): # real signature unknown; restored from __doc__ """ x.__delslice__(i, j) <==> del x[i:j] Use of negative indices is not supported. """ pass def __eq__(self, y): # real signature unknown; restored from __doc__ """ x.__eq__(y) <==> x==y """ pass def __getattribute__(self, name): # real signature unknown; restored from __doc__ """ x.__getattribute__('name') <==> x.name """ pass def __getitem__(self, y): # real signature unknown; restored from __doc__ """ x.__getitem__(y) <==> x[y] """ pass def __getslice__(self, i, j): # real signature unknown; restored from __doc__ """ x.__getslice__(i, j) <==> x[i:j] Use of negative indices is not supported. """ pass def __ge__(self, y): # real signature unknown; restored from __doc__ """ x.__ge__(y) <==> x>=y """ pass def __gt__(self, y): # real signature unknown; restored from __doc__ """ x.__gt__(y) <==> x>y """ pass def __iadd__(self, y): # real signature unknown; restored from __doc__ """ x.__iadd__(y) <==> x+=y """ pass def __imul__(self, y): # real signature unknown; restored from __doc__ """ x.__imul__(y) <==> x*=y """ pass def __init__(self, seq=()): # known special case of list.__init__ """ list() -> new empty list list(iterable) -> new list initialized from iterable's items # (copied from class doc) """ pass def __iter__(self): # real signature unknown; restored from __doc__ """ x.__iter__() <==> iter(x) """ pass def __len__(self): # real signature unknown; restored from __doc__ """ x.__len__() <==> len(x) """ pass def __le__(self, y): # real signature unknown; restored from __doc__ """ x.__le__(y) <==> x<=y """ pass def __lt__(self, y): # real signature unknown; restored from __doc__ """ x.__lt__(y) <==> x<y """ pass def __mul__(self, n): # real signature unknown; restored from __doc__ """ x.__mul__(n) <==> x*n """ pass @staticmethod # known case of __new__ def __new__(S, *more): # real signature unknown; restored from __doc__ """ T.__new__(S, ...) -> a new object with type S, a subtype of T """ pass def __ne__(self, y): # real signature unknown; restored from __doc__ """ x.__ne__(y) <==> x!=y """ pass def __repr__(self): # real signature unknown; restored from __doc__ """ x.__repr__() <==> repr(x) """ pass def __reversed__(self): # real signature unknown; restored from __doc__ """ L.__reversed__() -- return a reverse iterator over the list """ pass def __rmul__(self, n): # real signature unknown; restored from __doc__ """ x.__rmul__(n) <==> n*x """ pass def __setitem__(self, i, y): # real signature unknown; restored from __doc__ """ x.__setitem__(i, y) <==> x[i]=y """ pass def __setslice__(self, i, j, y): # real signature unknown; restored from __doc__ """ x.__setslice__(i, j, y) <==> x[i:j]=y Use of negative indices is not supported. """ pass def __sizeof__(self): # real signature unknown; restored from __doc__ """ L.__sizeof__() -- size of L in memory, in bytes """ pass __hash__ = None list