Question

我试图从循环中打印列表列表，但输出错误！附加到较大列表的最后一个列表是重复。

输出我期待：

FINAL LIST:
[[(1, 2), (2, 3)],
 [(2, 3), (3, 4)]]

我得到的输出：

FINAL LIST:
[[(2, 3), (3, 4)],
 [(2, 3), (3, 4)]]

我在这里做错了什么？这是我的代码：

a = []
count = 1

#Function that generates some nos. for the list
def func():

    del a[:]
    for i in range(count,count+2):
        x = i
        y = i+1
        a.append((x,y))
    print '\nIn Function:',a    #List seems to be correct here
    return a


#List of lists
List = []
for i in range(1,3):
    b = func()             #Calling Function
    print 'In Loop:',b     #Checking the value, list seems to be correct here also
    List.append(b)
    count = count+1


print '\nList of Lists:'
print List

Answer 1

您将相同的列表（a）多次附加到List（您可以使用print List[0] is List[1]查看）。您需要创建多个列表，如下例所示：

l = []
for i in xrange(3):
    l.append([i, i+1])
print l

Answer 2

问题在于del a[:]语句。剩下的代码很好。而不是这样做，在函数的开头放一个空的a列表，问题就消失了：

count = 1

#Function that generates some nos. for the list
def func():
    a = []
    for i in range(count,count+2):
        x = i
        y = i+1
        a.append((x,y))
    print '\nIn Function:',a    #List seems to be correct here
    return a


#List of lists
List = []
count = 1
for i in range(1,3):
    b = func()             #Calling Function
    print 'In Loop:',b     #Checking the value, list seems to be correct here also
    List.append(b)
    count = count + 1


print '\nList of Lists:'
print List

Python中的列表列表 - ＆gt;输出错误

2 个答案: