pandas dataframe: filtering on rows based on the string content of a column

Question

I use the following code to filter out some rows in my data frame:

my_df_1 = my_df[my_df.col1.startswith('good_')]

But I got the following errors:

AttributeErrorTraceback (most recent call last)
<ipython-input-3-dbd2d6731148> in <module>()
----> 1 my_df_1 = my_df[my_df.col1.startswith('good_')]

/usr/local/lib/python2.7/dist-packages/pandas/core/generic.pyc in __getattr__(self, name)
   2742             if name in self._info_axis:
   2743                 return self[name]
-> 2744             return object.__getattribute__(self, name)
   2745 
   2746     def __setattr__(self, name, value):

AttributeError: 'Series' object has no attribute 'starts with'

Does anyone know what I missed? Thanks!

Randy · Accepted Answer · 2016-12-12 04:51:49Z

2

You just need to add .str in there to use the Pandas string methods:

In [12]: df = pd.DataFrame({'s': ['good_1', 'bad_1', 'good_2']})

In [13]: df
Out[13]:
        s
0  good_1
1   bad_1
2  good_2

In [14]: df['s'].str.startswith("good_")
Out[14]:
0     True
1    False
2     True
Name: s, dtype: bool

In [15]: df[df['s'].str.startswith("good_")]
Out[15]:
        s
0  good_1
2  good_2

answered Dec 12, 2016 at 4:51

Randy

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