如何在 Python 中将 Pandas DataFrame 与 None 进行比较？
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How to compare pandas DataFrame against None in Python?
提问by CiaranWelsh
How do I compare a pandas DataFrame with None? I have a constructor that takes one of a parameter_fileor a pandas_dfbut never both.
如何将 Pandas DataFrame 与None? 我有一个构造函数，它采用 aparameter_file或 a之一，pandas_df但从不采用两者。
def __init__(self,copasi_file,row_to_insert=0,parameter_file=None,pandas_df=None):
self.copasi_file=copasi_file
self.parameter_file=parameter_file
self.pandas_df=pandas_df
However, when I later try to compare the pandas_dfagainst None, (i.e. when self.pandas_dfactually contains a pandas dataframe):
但是，当我稍后尝试比较pandas_df与None, 时（即self.pandas_df实际包含Pandas数据框时）：
if self.pandas_df!=None:
print 'Do stuff'
I get the following TypeError:
我收到以下类型错误：
File "C:\Anaconda1\lib\site-packages\pandas\core\internals.py", line 885, in eval
% repr(other))
TypeError: Could not compare [None] with block values
回答by Mike Müller
Use is not:
使用is not：
if self.pandas_df is not None:
print 'Do stuff'
PEP 8says:
PEP 8说：
Comparisons to singletons like
Noneshould always be done withisoris not, never the equality operators.
与单例的比较
None应该总是用isor来完成is not，而不是等号运算符。
There is also a nice explanationwhy.
还有一个很好的解释为什么。
