Python: Pandas Concatenate each row into a string

Question

I have the following Pandas Dataframe:

df=pd.DataFrame({0:["a","b","c","d"], 1:["e","f","g",None], 2:["h",None,None,None]})

   0     1     2
0  a     e     h
1  b     f  None
2  c     g  None
3  d  None  None

I like to create a new DataFrame with one column where each row is a concatenated string, with a seperator ",":

       0
0  a,e,h
1    b,f
2    c,g
3      d

For a single row I could use

df.iloc[0,:].str.cat(sep=",")

but how can I apply this to the whole DataFrame, without using a for-loop (if possible)

Answer 1

Stacking removes nulls by default. Follow-up with a groupby on level=0

df.stack().groupby(level=0).apply(','.join)

0    a,e,h
1      b,f
2      c,g
3        d
dtype: object

---

To duplicate OP's output, use to_frame

df.stack().groupby(level=0).apply(','.join).to_frame(0)

       0
0  a,e,h
1    b,f
2    c,g
3      d

Answer 2

for i, r in df.iterrows():
    print(r.str.cat(sep=","))

as a new dataframe:

ndf = pd.DataFrame([r.str.cat(sep=",") for i, r in df.iterrows()])
print(ndf)

       0
0  a,e,h
1    b,f
2    c,g
3      d