Trying to create a DataFrame from two lists and an array-CodePudding

I have two lists and an array that need to be transformed into a DataFrame. This is more or less what I have:

listA = ['a', 'b', 'c', 'd']
listB = ['x', 'y', 'z']

array = [[10, 11, 12], [20, 21, 22], [30, 31, 32], [40, 41, 42]]

I want my DataFrame to be like this:

I've tried creating the DataFrame by inserting the lists into

pd.Dataframe()

and then specifying what the column's name should be. But no luck so far.

CodePudding user response：

pd.MultiIndex.from_product helps here; it will take the cartesian product of two lists given and give a MultiIndex with 2 levels populated as such:

>>> pd.DataFrame(np.ravel(array),
                 index=pd.MultiIndex.from_product([listA, listB]), 
                 columns=["value"])
     value
a x     10
  y     11
  z     12
b x     20
  y     21
  z     22
c x     30
  y     31
  z     32
d x     40
  y     41
  z     42

values are the raveled (flattened) array
index is the product of the two lists
columns is the "value" which is the only one.

CodePudding user response：

out = pd.DataFrame(array, index=listA, columns=listB).stack()

out:

a  x    10
   y    11
   z    12
b  x    20
   y    21
   z    22
c  x    30
   y    31
   z    32
d  x    40
   y    41
   z    42
dtype: int64