Using rpy2 in Jupyter/IPython run_line_magic error - ipython

Question

In the IPython and Jupyter documentation it says that get_ipython().magic() is deprecated. But when I changed my code to use run_line_magic it is failing to push to R (see below). Might be related to this problem
https://bitbucket.org/rpy2/rpy2/issues/184/valueerror-call-stack-is-not-deep-enough
I'm on Mac Yosemite, using Anaconda with Python 2.7. I just updated both Anaconda and rpy2 yesterday. The code below is from a Jupyter notebook.
%load_ext rpy2.ipython
import pandas as pd
'''Two test functions with rpy2.
The only difference between them is that
rpy2fun_magic uses 'magic' to push variable to R and
rpy2fun_linemagic uses 'run_line_magic' to push variable.
'magic' works fine. 'run_line_magic' returns an error.'''
def rpy2fun_magic(df):
get_ipython().magic('R -i df')
get_ipython().run_line_magic('R','df_cor <- cor(df)')
get_ipython().run_line_magic('R','-o df_cor')
return (df_cor)
def rpy2fun_linemagic(df):
get_ipython().run_line_magic('R','-i df')
get_ipython().run_line_magic('R','df_cor <- cor(df)')
get_ipython().run_line_magic('R','-o df_cor')
return (df_cor)
dataframetest = pd.DataFrame([[1,2,3,4],[6,3,4,5],[9,1,7,3]])
df_cor_magic = rpy2fun_magic(dataframetest)
print 'Using magic to push variable works fine\n'
print df_cor_magic
print '\nBut using run_line_magic returns an error\n'
df_cor_linemagic = rpy2fun_linemagic(dataframetest)
Using magic to push variable works fine
[[ 1. -0.37115374 0.91129318 -0.37115374]
[-0.37115374 1. -0.72057669 1. ]
[ 0.91129318 -0.72057669 1. -0.72057669]
[-0.37115374 1. -0.72057669 1. ]]
But using run_line_magic returns an error
---------------------------------------------------------------------------
NameError Traceback (most recent call last)
<ipython-input-1-e418b72a8621> in <module>()
28 print '\nBut using run_line_magic returns an error\n'
29
---> 30 df_cor_linemagic = rpy2fun_linemagic(dataframetest)
<ipython-input-1-e418b72a8621> in rpy2fun_linemagic(df)
15
16 def rpy2fun_linemagic(df):
---> 17 get_ipython().run_line_magic('R','-i df')
18 get_ipython().run_line_magic('R','df_cor <- cor(df)')
19 get_ipython().run_line_magic('R','-o df_cor')
/Users/alexmillner/anaconda/lib/python2.7/site-packages/IPython/core/interactiveshell.pyc in run_line_magic(self, magic_name, line)
2255 kwargs['local_ns'] = sys._getframe(stack_depth).f_locals
2256 with self.builtin_trap:
-> 2257 result = fn(*args,**kwargs)
2258 return result
2259
/Users/alexmillner/anaconda/lib/python2.7/site-packages/rpy2/ipython/rmagic.pyc in R(self, line, cell, local_ns)
/Users/alexmillner/anaconda/lib/python2.7/site-packages/IPython/core/magic.pyc in <lambda>(f, *a, **k)
191 # but it's overkill for just that one bit of state.
192 def magic_deco(arg):
--> 193 call = lambda f, *a, **k: f(*a, **k)
194
195 if callable(arg):
/Users/alexmillner/anaconda/lib/python2.7/site-packages/rpy2/ipython/rmagic.pyc in R(self, line, cell, local_ns)
657 val = self.shell.user_ns[input]
658 except KeyError:
--> 659 raise NameError("name '%s' is not defined" % input)
660 if args.converter is None:
661 ro.r.assign(input, self.pyconverter(val))
NameError: name 'df' is not defined

Answer 1

Some discussion of the same issue with %timeit first, followed by workaround answers at the bottom. I'm using IPython 3.1.0 with Anaconda 2.7.10, so my observations below could be different based on version differences alone.
This is not unique to the R extension, you can reproduce this with something simpler like %timeit:
In [47]: dfrm
Out[47]:
A B C
0 0.690466 0.370793 0.963782
1 0.478427 0.358897 0.689173
2 0.189277 0.268237 0.570624
3 0.735665 0.342549 0.509810
4 0.929736 0.090079 0.384444
5 0.210941 0.347164 0.852408
6 0.241940 0.187266 0.961489
7 0.768143 0.548450 0.604004
8 0.055765 0.842224 0.668782
9 0.717827 0.047011 0.948673
In [48]: def run_timeit(df):
get_ipython().run_line_magic('timeit', 'df.sum()')
....:
In [49]: run_timeit(dfrm)
---------------------------------------------------------------------------
NameError Traceback (most recent call last)
<ipython-input-49-1e62302232b6> in <module>()
----> 1 run_timeit(dfrm)
<ipython-input-48-0a3e09ec1e0c> in run_timeit(df)
1 def run_timeit(df):
----> 2 get_ipython().run_line_magic('timeit', 'df.sum()')
3
/home/ely/anaconda/lib/python2.7/site-packages/IPython/core/interactiveshell.pyc in run_line_magic(self, magic_name, line)
2226 kwargs['local_ns'] = sys._getframe(stack_depth).f_locals
2227 with self.builtin_trap:
-> 2228 result = fn(*args,**kwargs)
2229 return result
2230
/home/ely/anaconda/lib/python2.7/site-packages/IPython/core/magics/execution.pyc in timeit(self, line, cell)
/home/ely/anaconda/lib/python2.7/site-packages/IPython/core/magic.pyc in <lambda>(f, *a, **k)
191 # but it's overkill for just that one bit of state.
192 def magic_deco(arg):
--> 193 call = lambda f, *a, **k: f(*a, **k)
194
195 if callable(arg):
/home/ely/anaconda/lib/python2.7/site-packages/IPython/core/magics/execution.pyc in timeit(self, line, cell)
1034 number = 1
1035 for _ in range(1, 10):
-> 1036 time_number = timer.timeit(number)
1037 worst_tuning = max(worst_tuning, time_number / number)
1038 if time_number >= 0.2:
/home/ely/anaconda/lib/python2.7/site-packages/IPython/core/magics/execution.pyc in timeit(self, number)
130 gc.disable()
131 try:
--> 132 timing = self.inner(it, self.timer)
133 finally:
134 if gcold:
<magic-timeit> in inner(_it, _timer)
NameError: global name 'df' is not defined
The issue is that the line magics are set to look for variable names at global scope, not at function scope. If the argument to your function rpy2fun_linemagic happened to coincide with a global variable name, the interior code would pick that up, for example:
In [52]: def run_timeit(dfrm):
get_ipython().run_line_magic('timeit', 'dfrm.sum()')
....:
In [53]: run_timeit(dfrm)
The slowest run took 5.67 times longer than the fastest. This could mean that an intermediate result is being cached
10000 loops, best of 3: 99.1 µs per loop
But this only works by accident, because the interior string passed to run_line_magic contains a name that is found globally.
However, I do get the same error even if using the plain magic function:
In [58]: def run_timeit(df):
get_ipython().magic('timeit df.sum()')
....:
In [59]: run_timeit(dfrm)
---------------------------------------------------------------------------
NameError Traceback (most recent call last)
<ipython-input-59-1e62302232b6> in <module>()
----> 1 run_timeit(dfrm)
<ipython-input-58-e98c720ea7e8> in run_timeit(df)
1 def run_timeit(df):
----> 2 get_ipython().magic('timeit df.sum()')
3
/home/ely/anaconda/lib/python2.7/site-packages/IPython/core/interactiveshell.pyc in magic(self, arg_s)
2305 magic_name, _, magic_arg_s = arg_s.partition(' ')
2306 magic_name = magic_name.lstrip(prefilter.ESC_MAGIC)
-> 2307 return self.run_line_magic(magic_name, magic_arg_s)
2308
2309 #-------------------------------------------------------------------------
/home/ely/anaconda/lib/python2.7/site-packages/IPython/core/interactiveshell.pyc in run_line_magic(self, magic_name, line)
2226 kwargs['local_ns'] = sys._getframe(stack_depth).f_locals
2227 with self.builtin_trap:
-> 2228 result = fn(*args,**kwargs)
2229 return result
2230
/home/ely/anaconda/lib/python2.7/site-packages/IPython/core/magics/execution.pyc in timeit(self, line, cell)
/home/ely/anaconda/lib/python2.7/site-packages/IPython/core/magic.pyc in <lambda>(f, *a, **k)
191 # but it's overkill for just that one bit of state.
192 def magic_deco(arg):
--> 193 call = lambda f, *a, **k: f(*a, **k)
194
195 if callable(arg):
/home/ely/anaconda/lib/python2.7/site-packages/IPython/core/magics/execution.pyc in timeit(self, line, cell)
1034 number = 1
1035 for _ in range(1, 10):
-> 1036 time_number = timer.timeit(number)
1037 worst_tuning = max(worst_tuning, time_number / number)
1038 if time_number >= 0.2:
/home/ely/anaconda/lib/python2.7/site-packages/IPython/core/magics/execution.pyc in timeit(self, number)
130 gc.disable()
131 try:
--> 132 timing = self.inner(it, self.timer)
133 finally:
134 if gcold:
<magic-timeit> in inner(_it, _timer)
NameError: global name 'df' is not defined
One (super bad) way to get around this is to use globals to locate the item that is the same as the argument that was passed to your function, and then you'll have a global name for it.
For example:
In [68]: def run_timeit(df):
for var_name, var_val in globals().iteritems():
if df is var_val:
get_ipython().run_line_magic('timeit', '%s.sum()'%(var_name))
break
....:
In [69]: run_timeit(dfrm)
The slowest run took 5.72 times longer than the fastest. This could mean that an intermediate result is being cached
10000 loops, best of 3: 99.2 µs per loop
But this is very unstable, since it relies on pass-by-name in Python. If I passed an object like an integer or string, I would have to check whether it was interned or something, but otherwise couldn't find it "by name" in the global namespace.
Another way to do it that might be slightly better is to use the user_ns namespace dict that IPython stores. Then at least you're not looking at globals, and there is more stability over specific variables that have been named when assigned by the user in IPython:
In [71]: def run_timeit(df):
....: g = get_ipython()
....: for var_name, var_val in g.user_ns.iteritems():
....: if df is var_val:
....: g.run_line_magic('timeit', '%s.sum()'%(var_name))
....: break
....:
In [72]: run_timeit(dfrm)
The slowest run took 5.58 times longer than the fastest. This could mean that an intermediate result is being cached
10000 loops, best of 3: 99 µs per loop
In the case of your specific R function call, I would try:
def rpy2fun_linemagic(df):
g = get_ipython()
for var_name, var_val in g.user_ns.iteritems():
if df is var_val:
g.run_line_magic('R', '-i %s'%(var_name))
g.run_line_magic('R', 'df_cor <- cor(%s)'%(var_name))
g.run_line_magic('R', '-o df_cor')
return df_cor
You might also have to be careful on the return statement. You might need to use return g.user_ns['df_cor'] or something if the result of the output conversion back to Python is to create the variable at global scope as well, rather than function scope. Or, if that variable gets created as a side effect, you may not want to return anything at all. I'm not a big fan of relying on implicit mutation like that, but it could work for you.

Answer 2

I suspect that the code example you are providing is there only to demonstrate the issue with run_line_magic(), but for reference I am adding a way to do the same without ipython being involved.
from rpy2.robjects import globalenv
def rpy2cor(df):
fun = globalenv.get('cor', wantfun=True)
df_cor = fun(df)
return df_cor