Rotate DataFrame in Pandas for output in CSV

Question

This is a simple question for which the answer is surprisingly hard to find on the Internet. Here's the situation:

>>> A [('hey', 'you', 4), ('hey', 'not you', 5), ('not hey', 'you', 2), ('not hey', 'not you', 6)] >>> A_p = pandas.DataFrame(A) >>> A_p 0 1 2 0 hey you 4 1 hey not you 5 2 not hey you 2 3 not hey not you 6 >>> B_p = A_p.pivot(0,1,2) >>> B_p 1 not you you 0 hey 5 4 not hey 6 2 

This is not exactly what is suggested in the documentation for pivot - there, it shows the results without 1 and 0 in the upper left corner. And this is what I am looking for, a DataFrame object that prints like

  not you you hey 5 4 not hey 6 2 

The problem is that normal behavior leads to the creation of a csv file whose first line

 0,not you,you 

when i really want

 not you, you 

When a normal csv file (with the previous “0”) reads into R, it incorrectly sets the column and row names from the frame object, which leads to painful manual manipulations to get it in the correct format. Is there a way to get the anchor point to give me a DataFrame object without additional information in the upper left corner?

Answer 1

Well, you have:

 In [17]: B_p.to_csv(sys.stdout) 0,not you,you hey,5.0,4.0 not hey,6.0,2.0 In [18]: B_p.to_csv(sys.stdout, index=False) not you,you 5.0,4.0 6.0,2.0 

But I guess you need line names. Setting the index name to None ( B_p.index.name = None ) gives a leading comma:

 In [20]: B_p.to_csv(sys.stdout) ,not you,you hey,5.0,4.0 not hey,6.0,2.0 

This roughly matches (ignoring quoted strings) what R writes to write.csv when row.names=TRUE :

 "","a","b" "foo",0.720538259472741,-0.848304940318957 "bar",-0.64266667412325,-0.442441171401282 "baz",-0.419181615269841,-0.658545964124229 "qux",0.881124313748992,0.36383198969179 "bar2",-1.35613767310069,-0.124014006180608 

Any of them help?

EDIT: added option index_label=False , which does what you want:

 In [2]: df Out[2]: AB one 1 4 two 2 5 three 3 6 In [3]: df.to_csv('foo.csv', index_ index_exp index_label= index_name= In [3]: df.to_csv('foo.csv', index_name=False) In [4]: 11:24 ~/code/pandas (master)$ R R version 2.14.0 (2011-10-31) Copyright (C) 2011 The R Foundation for Statistical Computing ISBN 3-900051-07-0 Platform: x86_64-unknown-linux-gnu (64-bit) R is free software and comes with ABSOLUTELY NO WARRANTY. You are welcome to redistribute it under certain conditions. Type 'license()' or 'licence()' for distribution details. Natural language support but running in an English locale R is a collaborative project with many contributors. Type 'contributors()' for more information and 'citation()' on how to cite R or R packages in publications. Type 'demo()' for some demos, 'help()' for on-line help, or 'help.start()' for an HTML browser interface to help. Type 'q()' to quit R. [Previously saved workspace restored] re> read.csv('foo.csv') AB one 1 4 two 2 5 three 3 6