How to create a edgelist from a pandas datrafame?

Question

I have a pandas dataframe (df) with 1: connected vertices and 0: unconnected vertices

X	B	C	D
F	1	1	0
G	0	0	1
H	0	1	0

I need to convert this to a edgelist like:

Source	Target
F	B
F	C
G	D
H	C

What is the best way to do this?

Answer 1

Here is a way using stack() and constructing a new df.

df2 = (pd.DataFrame(
    df.set_index('X').where(lambda x: x.ne(0)).stack().index.tolist(),
    columns = ['X','Target']))

or

df.set_index('X').mul(df.columns[1:]).where(lambda x: x.ne('')).stack().droplevel(1).reset_index().set_axis(['X','Target'],axis=1)

or

df.set_index('X').dot(df.columns[1:] + ',').str.strip(',').str.split(',').explode().reset_index().set_axis(['X','Target'],axis=1)

Output:

   X Target
0  F      B
1  F      C
2  G      D
3  H      C