How to overcome TypeError unhashable type list

Question

I m trying to take a file that looks like this  AAA x 111 AAB x 111 AAA x 112 AAC x 123      And use a dictionary to so that the output looks like this  AAA    111    112    AAB    111    AAC   123         This is what I ve tried file   open  quot filename txt quot    quot r quot    readline   file readline   rstrip   while readline    quot  quot       list          list   readline split  quot   quot       j   list index  quot x quot       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    I keep getting a TypeError  unhashable type   list   I know that keys in a dictionary can t be lists but I m trying to make my value into a list not the key  I m wondering if I made a mistake somewhere

User · Answer

You re trying to use k  which is a list  as a key for d  Lists are mutable and can t be used as dict keys   Also  you re never initializing the lists in the dictionary  because of this line   if k not in d    False    Which should be   if k not in d    True    Which should actually be   if k not in d

User · Answer

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    Hash values are just integers which are used to compare dictionary keys during a dictionary lookup quickly   Internally  hash   method calls   hash     method of an object which are set by default for any object   Converting a nested list to a set   gt  gt  gt  a    1 2 3 4  5 6 7  8 9   gt  gt  gt  set a  Traceback  most recent call last     File   lt stdin gt    line 1  in  lt module gt  TypeError  unhashable type   list    This happens because of the list inside a list which is a list which cannot be hashed  Which can be solved by converting the internal nested lists to a tuple    gt  gt  gt  set  1  2  3  4   5  6  7   8  9   set  1  2  3  4  8  9   5  6  7      Explicitly hashing a nested list   gt  gt  gt  hash  1  2  3   4  5    6  7   Traceback  most recent call last     File   lt stdin gt    line 1  in  lt module gt  TypeError  unhashable type   list     gt  gt  gt  hash tuple  1  2  3   4  5    6  7    Traceback  most recent call last     File   lt stdin gt    line 1  in  lt module gt  TypeError  unhashable type   list    gt  gt  gt  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

User · Answer

The reason you re getting the unhashable type   list  exception is because k   list 0 j  sets k to be a  quot slice quot  of the list  which is logically another  often shorter  list  What you need is to get just the first item in list  written like so k   list 0   The same for v   list j   1   which should just be v   list 2  for the third element of the list returned from the call to readline split  quot   quot    I noticed several other likely problems with the code  of which I ll mention a few  A big one is you don t want to  re initialize d with d      for each line read in the loop  Another is it s generally not a good idea to name variables the same as any of the built-ins types because it ll prevent you from being able to access one of them if you need it     and it s confusing to others who are used to the names designating one of these standard items  For that reason  you ought to rename your variable list variable something different to avoid issues like that  Here s a working version of your with these changes in it  I also replaced the if statement expression you used to check to see if the key was already in the dictionary and now make use of a dictionary s setdefault   method to accomplish the same thing a little more succinctly  d      with open  quot nameerror txt quot    quot r quot   as file      line   file readline   rstrip       while line          lst   line split     Split into sequence like   AAA    x    111            k     v   lst  3     Get first and third items          d setdefault k      append v          line   file readline   rstrip    print  d      format d    Output  d    AAA     111    112     AAC     123     AAB     111

User · Answer

The TypeError is happening because k is a list  since it is created using a slice from another list with the line k   list 0 j    This should probably be something like k       join list 0 j    so you have a string instead   In addition to this  your if statement is incorrect as noted by Jesse s answer  which should read if k not in d or if not k in d  I prefer the latter    You are also clearing your dictionary on each iteration since you have d      inside of your for loop   Note that you should also not be using list or file as variable names  since you will be masking builtins   Here is how I would rewrite your code   d      with open  filename txt    r   as input file      for line in input file          fields   line split           j   fields index  x           k       join fields  j           d setdefault k      append     join fields j 1       The dict setdefault   method above replaces the if k not in d logic from your code

User · Answer

python 3 2      with open  d   test txt   as f                k    i split   n    0  rstrip    split   for i in f readlines                  d                  for i   v in k                        d setdefault i     append v

User · Answer

As indicated by the other answers  the error is to due to k   list 0 j   where your key is converted to a list  One thing you could try is reworking your code to take advantage of the split function     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      Note that if you are using Python 3 x  you ll have to make a minor adjustment to get it work properly  If you open the file with rb  you ll need to use line   line split b x    which makes sure you are splitting the byte with the proper type of string   You can also open the file using with open  filename txt    rU   as f   or even with open  filename txt    r   as f   and it should work fine

[python] How to overcome TypeError: unhashable type: 'list'

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