iterrows pandas get next rows value

Question

I have a df in pandas

import pandas as pd
df = pd.DataFrame(['AA', 'BB', 'CC'], columns = ['value'])

I want to iterate over rows in df. For each row i want rows value and next rows value Something like(it does not work):

for i, row in df.iterrows():
     print row['value']
     i1, row1 = next(df.iterrows())
     print row1['value']

As a result I want

'AA'
'BB'
'BB'
'CC'
'CC'
*Wrong index error here  

At this point i have mess way to solve this

for i in range(0, df.shape[0])
   print df.irow(i)['value']
   print df.irow(i+1)['value']

Is there more efficient way to solve this issue?

Answer 1

Firstly, your "messy way" is ok, there's nothing wrong with using indices into the dataframe, and this will not be too slow. iterrows() itself isn't terribly fast.

A version of your first idea that would work would be:

row_iterator = df.iterrows()
_, last = row_iterator.next()  # take first item from row_iterator
for i, row in row_iterator:
    print(row['value'])
    print(last['value'])
    last = row

The second method could do something similar, to save one index into the dataframe:

last = df.irow(0)
for i in range(1, df.shape[0]):
    print(last)
    print(df.irow(i))
    last = df.irow(i)

When speed is critical you can always try both and time the code.