python - Is this a bug in Pandas? FloatingPointError on ewm().std() -

when execute following, floatingpointerror.

import traceback import warnings import sys import pandas pd import numpy np np.seterr(all='raise') def warn_with_traceback(message, category, filename, lineno, file=none, line=none):     traceback.print_stack()     log = file if hasattr(file,'write') else sys.stderr     log.write(warnings.formatwarning(message, category, filename, lineno, line))  warnings.showwarning = warn_with_traceback  pd.series(np.random.randn(50)).pct_change().ewm(span=35, min_periods=35).std() 

i following error:

floatingpointerrortraceback (most recent call last) <ipython-input-2-3db1ff4816cf> in <module>() ----> 1 pd.series(np.random.randn(50)).pct_change().ewm(span=35, min_periods=35).std()  /projects/anaconda3/lib/python3.5/site-packages/pandas/core/window.py in std(self, bias, **kwargs)    1285     def std(self, bias=false, **kwargs):    1286         """exponential weighted moving stddev""" -> 1287         return _zsqrt(self.var(bias=bias, **kwargs))    1288     1289     vol = std  /projects/anaconda3/lib/python3.5/site-packages/pandas/core/window.py in _zsqrt(x)    1487 def _zsqrt(x):    1488     result = np.sqrt(x) -> 1489     mask = x < 0    1490     1491     pandas import dataframe  /projects/anaconda3/lib/python3.5/site-packages/pandas/core/ops.py in wrapper(self, other, axis)     761                 other = np.asarray(other)     762  --> 763             res = na_op(values, other)     764             if isscalar(res):     765                 raise typeerror('could not compare %s type series' %  /projects/anaconda3/lib/python3.5/site-packages/pandas/core/ops.py in na_op(x, y)     714      715             try: --> 716                 result = getattr(x, name)(y)     717                 if result notimplemented:     718                     raise typeerror("invalid type comparison")  floatingpointerror: invalid value encountered in less 

why getting these warnings? bug in pandas? how can sure calculations correct?

np.seterr(all='raise') causing issue.

check out: pandas: floatingpointerror np.seterr(all='raise') , missing data

the output of pd.series(np.random.randn(50)).pct_change().ewm(span=35, min_periods=35).std() without np.seterr(all='raise') is:

0          nan 1          nan 2          nan 3          nan 4          nan 5          nan 6          nan 7          nan 8          nan 9          nan 10         nan 11         nan 12         nan 13         nan 14         nan 15         nan 16         nan 17         nan 18         nan 19         nan 20         nan 21         nan 22         nan 23         nan 24         nan 25         nan 26         nan 27         nan 28         nan 29         nan 30         nan 31         nan 32         nan 33         nan 34         nan 35    9.927862 36    9.636469 37    9.360825 38    9.061078 39    8.792150 40    8.549347 41    8.284875 42    8.026411 43    7.779943 44    7.563633 45    7.331553 46    7.114672 47    6.898717 48    6.716513 49    6.514064 dtype: float64