BUG: series update

[midfield]

import pandas as pd

df = pd.DataFrame(dict((c, [1,2,3]) for c in ['a', 'b', 'c']))
df.set_index(['a', 'b', 'c'], inplace=True)
s = pd.Series([1], index=[(2,2,2)])
df['val'] = 0
df
df['val'].update(s)
df

on my machine (pandas 0.11.1.dev-45d298d, linux) i get the rather unexpected output

                       val
a b c
1 1 1                    0
2 2 2  4607182418800017408
3 3 3                    0

[midfield]

sorry i'm having trouble reproducing right now, let me double check.

[midfield]

i had a typo in the code, try it now.

[jtratner]

Yep - I see this on master. Hmmm...

[jtratner]

Now I'm only seeing it intermittently :(

[jtratner]

nvm, I see it consistently now...

[cpcloud]

figured out the issue...it's in common._maybe_upcast_putmask.

ipdb> p r
array([ 0.,  1.,  0.])
ipdb> result
array([0, 0, 0])
ipdb> result.view(float)
array([ 0.,  0.,  0.])
ipdb> p r.view(int)
array([                  0, 4607182418800017408,                   0])

[jreback]

yep...had this bug elsewhere...pr soon

[cpcloud]

i think this is the problem

                change.dtype = r.dtype
                change[:] = r

[cpcloud]

@jreback do u mind if i take this one?

[cpcloud]

oh darn

[jreback]

this is actually quite non-trivial. The existing code works fine, but the parent DataFrame needs a way to update the blocks, related to #3970 (though that had more to do with a bug in consolidation)

[cpcloud]

reback-fu is what we should start calling ur prs

[wesm]

In place dtype changes are a nono. We need to find a better way

[jreback]

Inplace dtype changes are required on an int series (though pretty rare), when converting to floats (or it simply doesn't change).....this can be fixed (I think) when Series is inhertited from NDFrame; then its the same as dtype changes in Frame, just replace the innarrds and return, the top-level object is unchanged.

currently the dtype HAS to change inplace because the user has a reference to the Series

not saying that this is a great solution, but only one currently

[jreback]

closed by #3482