Python[四]:List and stack

 

1.List和stack

list.append(x)

Add an item to the end of the list; equivalent to a[len(a):] = [x].

list.extend(L)

Extend the list by appending all the items in the given list; equivalent to a[len(a):] = L.

list.insert(i, x)

Insert an item at a given position. The first argument is the index of the element before which to insert, soa.insert(0, x) inserts at the front of the list, and a.insert(len(a), x) is equivalent to a.append(x).

list.remove(x)

Remove the first item from the list whose value is x. It is an error if there is no such item.

list.pop([i])

Remove the item at the given position in the list, and return it. If no index is specified, a.pop() removes and returns the last item in the list. (The square brackets around the i in the method signature denote that the parameter is optional, not that you should type square brackets at that position. You will see this notation frequently in the Python Library Reference.)

list.index(x)

Return the index in the list of the first item whose value is x. It is an error if there is no such item.

list.count(x)

Return the number of times x appears in the list.

list.sort()

Sort the items of the list, in place.

list.reverse()

Reverse the elements of the list, in place.

Using Lists as Stacks

The list methods make it very easy to use a list as a stack, where the last element added is the first element retrieved (“last-in, first-out”). To add an item to the top of the stack, use append(). To retrieve an item from the top of the stack, use pop() without an explicit index.

 

 

>>> a=[66.25,333,333,1,1234.5]>>> print(a.count())Traceback (most recent call last): File "<pyshell#59>", line 1, in <module> print(a.count())TypeError: count() takes exactly one argument (0 given)>>> print(a.count(333))2>>> print(a.count()'x')SyntaxError: invalid syntax (<pyshell#61>, line 1)>>> print(a.count('x'))0>>> a.append(333)>>> a[66.25, 333, 333, 1, 1234.5, 333]>>> print(a.count(333))3>>> a.index(333)1>>> a.remove(333)>>> a[66.25, 333, 1, 1234.5, 333]>>> a[66.25, 333, 1, 1234.5, 333]>>> a.reverse()>>> a[333, 1234.5, 1, 333, 66.25]>>> a.sort()>>> a[1, 66.25, 333, 333, 1234.5]>>> stack=[3,4,5]>>> stack.append(6)>>> stack.append(7)>>> stack[3, 4, 5, 6, 7]>>> stack.pop<built-in method pop of list object at 0x01387648>>>> stack.pop()7>>> stack[3, 4, 5, 6]>>> stack.pop()6>>> stack[3, 4, 5]>>> stack.pop()5>>> stack[3, 4]>>>>>> queue=['Tom','Rick','Tim']>>> queue.append('Terry')>>> queue.append('QiQi')>>> queue['Tom', 'Rick', 'Tim', 'Terry', 'QiQi']>>> queue.pop(0)'Tom'>>> queue['Rick', 'Tim', 'Terry', 'QiQi']>>> queue.opo(0)Traceback (most recent call last): File "<pyshell#91>", line 1, in <module> queue.opo(0)AttributeError: 'list' object has no attribute 'opo'>>> queue.pop(0)'Rick'>>> queue['Tim', 'Terry', 'QiQi']>>>>>> vec=[2,4,6]>>> [3*x for x in vec][6, 12, 18]>>> [[x,x**2] for x in vec][[2, 4], [4, 16], [6, 36]]>>> freshfruit=[' banana',' loganbery ','possin fruit ']>>> [weapon.strip() for weapon in freshfruit]['banana', 'loganbery', 'possin fruit']>>> [3*x for x in vec if x>3][12, 18]>>> [3* x for x in vec if x<2][]>>> [x,x**2 for x in vec]SyntaxError: invalid syntax (<pyshell#101>, line 1)>>> [(x,x**2) for x in vec][(2, 4), (4, 16), (6, 36)]>>> vec1=[2,4,6]>>> vec2=[4,3,-9]>>> [x*y for x in vec1 for y in vec2][8, 6, -18, 16, 12, -36, 24, 18, -54]>>> [x+y for x in vec1 for y in vec2][6, 5, -7, 8, 7, -5, 10, 9, -3]>>> [vec[i]*vec[i] for i in range(len(vec1))][4, 16, 36]>>> [vec1[i]*vec[i] for i in range(len(vec1))][4, 16, 36]>>> [vec1[i]*vec[i] for i in range(len(vec2))][4, 16, 36]>>> [vec1[i]*vec2[i] for i in range(len(vec1))][8, 12, -54]>>> [str(round(355/113,i)) for i in range(1,6)]['3.1', '3.14', '3.142', '3.1416', '3.14159']>>> [str(round(355/113,i)) for i in range(6)]['3.0', '3.1', '3.14', '3.142', '3.1416', '3.14159']>>> [str(round(355/113,i)) for i in range(1,6,2)]['3.1', '3.142', '3.14159']