CODEWITHSUNDEEP
pythonpandasdataframeindexingrow
PParker
PParker

Reputation: 1511

Function to move specific row to top or bottom of pandas dataframe

I have two functions which shift a row of a pandas dataframe to the top or bottom, respectively. After applying them more then once to a dataframe, they seem to work incorrectly.

These are the 2 functions to move the row to top / bottom:

def shift_row_to_bottom(df, index_to_shift):
  """Shift row, given by index_to_shift, to bottom of df."""
  
  idx = df.index.tolist()
  idx.pop(index_to_shift)
  df = df.reindex(idx + [index_to_shift])
  
  return df


def shift_row_to_top(df, index_to_shift):
  """Shift row, given by index_to_shift, to top of df."""
  
  idx = df.index.tolist()
  idx.pop(index_to_shift)
  df = df.reindex([index_to_shift] + idx)
  
  return df

Note: I don't want to reset_index for the returned df.

Example:

df = pd.DataFrame({'Country' : ['USA', 'GE', 'Russia', 'BR', 'France'], 
                   'ID' : ['11', '22', '33','44', '55'],
                   'City' : ['New-York', 'Berlin', 'Moscow', 'London', 'Paris'],
                   'short_name' : ['NY', 'Ber', 'Mosc','Lon', 'Pa']
                  })
df =

    Country  ID  City    short_name
0   USA      11  New-York   NY
1   GE       22  Berlin     Ber
2   Russia   33  Moscow     Mosc
3   BR       44  London     Lon
4   France   55  Paris      Pa

This is my dataframe:

Now, apply function for the first time. Move row with index 0 to bottom:

df_shifted = shift_row_to_bottom(df,0)

df_shifted = 
Country     ID  City      short_name
1   GE      22  Berlin    Ber
2   Russia  33  Moscow    Mosc
3   BR      44  London    Lon
4   France  55  Paris     Pa
0   USA     11  New-York  NY

The result is exactly what I want.

Now, apply function again. This time move row with index 2 to the bottom:

df_shifted = shift_row_to_bottom(df_shifted,2)

df_shifted =
Country     ID  City    short_name
1   GE      22  Berlin    Ber
2   Russia  33  Moscow    Mosc
4   France  55  Paris     Pa
0   USA     11  New-York  NY
2   Russia  33  Moscow    Mosc

Well, this is not what I was expecting. There must be a problem when I want to apply the function a second time. The promblem is analog to the function shift_row_to_top.

My question is:

Upvotes: 2

Views: 2508

Answers (1)

Quang Hoang
Quang Hoang

Reputation: 150745

Your problem is these two lines:

  idx = df.index.tolist()
  idx.pop(index_to_shift)

idx is a list and idx.pop(index_to_shift) removes the item at index index_to_shift of idx, which is not necessarily valued index_to_shift as in the second case.

Try this function:

def shift_row_to_bottom(df, index_to_shift):
    idx = [i for i in df.index if i!=index_to_shift]
    return df.loc[idx+[index_to_shift]]

# call the function twice
for i in range(2): df = shift_row_to_bottom(df, 2)

Output:

  Country  ID      City short_name
0     USA  11  New-York         NY
1      GE  22    Berlin        Ber
3      BR  44    London        Lon
4  France  55     Paris         Pa
2  Russia  33    Moscow       Mosc

Upvotes: 1

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