Construct pandas DataFrame from list of tuples of row col values

Question

I have a list of tuples like  data       r1    c1   avg11  stdev11     r1    c2   avg12  stdev12     r2    c1   avg21  stdev21     r2    c2   avg22  stdev22      and I would like to put them into a pandas DataFrame with rows named by the first column and columns named by the 2nd column  It seems the way to take care of the row names is something like pandas DataFrame  x 1   for x in data   index    x 0  for x in data   but how do I take care of the columns to get a 2x2 matrix  the output from the previous set is 3x4   Is there a more intelligent way of taking care of row labels as well  instead of explicitly omitting them   EDIT It seems I will need 2 DataFrames - one for averages and one for standard deviations  is that correct  Or can I store a list of values in each  cell

User · Answer

I submit that it is better to leave your data stacked as it is:

df = pandas.DataFrame(data, columns=['R_Number', 'C_Number', 'Avg', 'Std'])

# Possibly also this if these can always be the indexes:
# df = df.set_index(['R_Number', 'C_Number'])

Then it's a bit more intuitive to say

df.set_index(['R_Number', 'C_Number']).Avg.unstack(level=1)

This way it is implicit that you're seeking to reshape the averages, or the standard deviations. Whereas, just using pivot, it's purely based on column convention as to what semantic entity it is that you are reshaping.

User · Answer

You can pivot your DataFrame after creating    gt  gt  gt  df   pd DataFrame data   gt  gt  gt  df pivot index 0  columns 1  values 2    avg DataFrame 1      c1     c2 0                r1  avg11  avg12 r2  avg21  avg22  gt  gt  gt  df pivot index 0  columns 1  values 3    stdev DataFrame 1        c1       c2 0                    r1  stdev11  stdev12 r2  stdev21  stdev22

User · Answer

This is what I expected to see when I came to this question      usr bin env python  import pandas as pd   df   pd DataFrame   1  2  3  4                       5  6  7  8                       9  0  1  2                       3  4  5  6                      columns list  abcd                      index   India    France    England    Germany    print df    gives           a  b  c  d India    1  2  3  4 France   5  6  7  8 England  9  0  1  2 Germany  3  4  5  6

[python] Construct pandas DataFrame from list of tuples of (row,col,values)

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