Python:TypeError:unshable type:'list'

Question

我在试着拿一个像这样的文件

AAA x 111
AAB x 111
AAA x 112
AAC x 123
...

并使用字典使输出如下所示

{AAA: ['111', '112'], AAB: ['111'], AAC: [123], ...}

这是我试过的

file = open("filename.txt", "r") 
readline = file.readline().rstrip()
while readline!= "":
    list = []
    list = readline.split(" ")
    j = list.index("x")
    k = list[0:j]
    v = list[j + 1:]
    d = {}
    if k not in d == False:
        d[k] = []
    d[k].append(v)
    readline = file.readline().rstrip()

我总是得到一个TypeError: unhashable type: 'list'。我知道字典中的键不能是列表，但我试图使我的值变成列表而不是键。我想知道我是不是在什么地方犯了错误。

Answer 1

如其他答案所示，错误是由于k = list[0:j]，在这里您的密钥被转换为列表。您可以尝试的一件事是重新编写代码以利用split函数：

# Using with ensures that the file is properly closed when you're done
with open('filename.txt', 'rb') as f:
  d = {}
  # Here we use readlines() to split the file into a list where each element is a line
  for line in f.readlines():
    # Now we split the file on `x`, since the part before the x will be
    # the key and the part after the value
    line = line.split('x')
    # Take the line parts and strip out the spaces, assigning them to the variables
    # Once you get a bit more comfortable, this works as well:
    # key, value = [x.strip() for x in line] 
    key = line[0].strip()
    value = line[1].strip()
    # Now we check if the dictionary contains the key; if so, append the new value,
    # and if not, make a new list that contains the current value
    # (For future reference, this is a great place for a defaultdict :)
    if key in d:
      d[key].append(value)
    else:
      d[key] = [value]

print d
# {'AAA': ['111', '112'], 'AAC': ['123'], 'AAB': ['111']}

请注意，如果您使用的是Python3.x，则必须进行一些小的调整才能使其正常工作。如果使用rb打开文件，则需要使用line = line.split(b'x')（这确保使用正确类型的字符串分割字节）。您还可以使用with open('filename.txt', 'rU') as f:（甚至with open('filename.txt', 'r') as f:）打开文件，它应该可以正常工作。

Answer 2

您试图使用k（这是一个列表）作为d的键。列表是可变的，不能用作dict键。

另外，由于这一行，您永远不会初始化字典中的列表：

if k not in d == False:

应该是：

if k not in d == True:

实际上应该是：

if k not in d:

Answer 3

Note: This answer does not explicitly answer the asked question. the other answers do it. Since the question is specific to a scenario and the raised exception is general, This answer points to the general case.

哈希值只是整数，用于在字典查找过程中快速比较字典键。

在内部，hash()方法调用默认为任何对象设置的对象的__hash__()方法。

将嵌套列表转换为集合

>>> a = [1,2,3,4,[5,6,7],8,9]
>>> set(a)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: unhashable type: 'list'

这是因为列表中的列表是无法散列的列表。这可以通过将内部嵌套列表转换为元组来解决

>>> set([1, 2, 3, 4, (5, 6, 7), 8, 9])
set([1, 2, 3, 4, 8, 9, (5, 6, 7)])

显式散列嵌套列表

>>> hash([1, 2, 3, [4, 5,], 6, 7])
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: unhashable type: 'list'


>>> hash(tuple([1, 2, 3, [4, 5,], 6, 7]))
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: unhashable type: 'list'

>>> hash(tuple([1, 2, 3, tuple([4, 5,]), 6, 7]))
-7943504827826258506

The solution to avoid this error is to restructure the list to have nested tuples instead of lists.