如何将字典列表写为csv

Question

I have a dictionary, in which for each key exists lists of (possible empty) lists. Now I want to write them in a csv file.

Dictionary:

d = {'A' : [['a', 'b'], ['a', 't', 'c']],[[],['a','b']]
     'B' : [['c', 'd'], ['e']],[['f', 'g'], ['c', 'd', 'e']]}

Furthermore I know that the first list of 'A' is related to the first list of 'B', the second of 'A' to the second of 'B' and so on. Wished Output: csv file looking like:

A , B 
a , c
b , d

a , e
t ,
c , 

  , f
  , g

a , c
b , d
  , e

All I tried so far was super "inconvenient" and didn't work in the end.

Answer 1

I have modified you Dic variable to look like this so that it is valid:

d = {'A' : [['a', 'b'], ['a', 't', 'c'],[],['a','b']],
     'B' : [['c', 'd'], ['e'],['f', 'g'], ['c', 'd', 'e']]}

The following code will do the pair wise matching you want over the elements of the list in each dict entry.

import itertools

with open('file.csv', 'w') as fid:            
    fid.write("{} , {}\n".format(*d.keys()))
    # first let's iterate over the element in the lists in d['a'] and d['b']
    # A and B will be matched sublists
    for A, B in itertools.zip_longest(d['A'],d['B'], fillvalue=''):
        # next iterate over the elements in the sub lists.  
        # Each pair will be an entry you want to write to your file
        for pair in itertools.zip_longest(A, B, fillvalue=''):                        
            fid.write("{} , {}\n".format(*pair))
        fid.write('\n')

zip_longest is the magic sauce here. It does the pair wise matching that you want. It will terminate when the end of the longest list is reached (as opposed to just zip which will terminates when the end of the shortest list is reached.

Content of file.csv:

A , B
a , c
b , d

a , e
t , 
c , 

 , f
 , g

a , c
b , d
 , e

Answer 2

A hand made solution, with pure python tools :

Dic = {'A' : [['a', 'b'], ['a', 't', 'c'],[],['a','b']],
       'B' : [['c', 'd'], ['e'],['f', 'g'], ['c', 'd', 'e']]}


with open('out.csv','w') as f:
    print(*Dic,sep=',',file=f) # keys
    for A,B in zip(*Dic.values()):
        for i in range(max(len(A),len(B))):
            print(A[i] if i<len(A) else ' ',end=',',file=f) 
            print(B[i] if i<len(B) else ' ',        file=f) 
        print(file=f) # blank line

For

A,B
a,c
b,d

a,e
t, 
c, 

 ,f
 ,g

a,c
b,d
 ,e