How to transform dataframe to from-to pairs?

user_3225309 0
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If I have a dataframe:

>>> import pandas as pd
>>> df = pd.DataFrame([
...     ['A', 'B', 'C', 'D'],
...     ['E', 'B', 'C']
... ])
>>> df
   0  1  2     3
0  A  B  C     D
1  E  B  C  None
>>>

I shoudl transform the dataframe to two columns format:

x, y
-----
A, B
B, C
C, D
E, B
B, C

For each row, from left to right, take two neighbor values and make a pair of it. It is kind of from-to if you consider each row as a path.

How to do the transformation?

pandas shift transformation python
2 Answers

We can do explode with zip 

s=pd.DataFrame(df.apply(lambda x : list(zip(x.dropna()[:-1],x.dropna()[1:])),axis=1).explode().tolist())
Out[336]: 
   0  1
0  A  B
1  B  C
2  C  D
3  E  B
4  B  C

Update 

s=df.apply(lambda x : list(zip(x.dropna()[:-1],x.dropna()[1:])),axis=1).explode()
s=pd.DataFrame(s.tolist(),index=s.index)

s
Out[340]: 
   0  1
0  A  B
0  B  C
0  C  D
1  E  B
1  B  C
user_79645270

Pre-preparing the data could help too:

import pandas as pd

inp = [['A', 'B', 'C', 'D'],
       ['E', 'B', 'C']]

# Convert beforehand
inp2 = [[[i[k], i[k+1]] for k in range(len(i)-1)] for i in inp]
inp2 = inp2[0] + inp2[1]

df = pd.DataFrame(inp2)
print(df)

Output:

   0  1
0  A  B
1  B  C
2  C  D
3  E  B
4  B  C
user_124894380
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