pandas updating column value using isin and loc

Question

I trying to update column in data frame one same as herehttp://stackoverflow.com/questions/24768657/replace-column-values-based-on-another-dataframe-python-pandas-better-way. However i am not able to do so -

df = pd.read_csv('Analyzed_test.csv')
df['rule_prediction'] = " " # created a column
a1 = pd.read_csv('D:\Junk\ML\\files\\Analyzed_rule1.csv')
a2 = pd.read_csv('D:\Junk\ML\\files\\Analyzed_rule2.csv')
a3 = pd.read_csv('D:\Junk\ML\\files\\Analyzed_rule3.csv')
a4 = pd.read_csv('D:\Junk\ML\\files\\Analyzed_rule4.csv')

df.loc[df.ID.isin(a1.ID), ['rule_prediction']] = a1[['rule_prediction']]
df.loc[df.ID.isin(a2.ID), ['rule_prediction']] = a2[['rule_prediction']]
df.loc[df.ID.isin(a3.ID), ['rule_prediction']] = a3[['rule_prediction']]
df.loc[df.ID.isin(a4.ID), ['rule_prediction']] = a4[['rule_prediction']]

#print t.count
#print self.df.head()
df.to_csv('D:\Junk\ML\\files\\output.csv')

When i open output.csv i see no values populated.

Columns in Analyzed_rule[1-4].csv dataframe in Analyzed_rule1.csv

The one i want to update is - Analyzed_test.csv to output.csv based on ID columns matched.

Thanks in advance.

You question looks like a [XY problem](http://meta.stackexchange.com/a/66378)... Can you post a sample data set, short explanation about what do you want to change/update and a desired resulting data set? — MaxU - stand with Ukraine, Oct 18 '16 at 18:12
ID |s rule_prediction LP001153 N LP001361 N LP001599 Y LP001652 N LP001867 Y LP001886 Y LP002042 Y LP002069 N LP002183 Y LP002412 Y LP002415 N LP002482 Y LP002747 N LP002858 N LP002867 Y LP002901 N — SKU_MIG, Oct 18 '16 at 18:14
Could you [post it in your question](http://stackoverflow.com/posts/40114807/edit)? — MaxU - stand with Ukraine, Oct 18 '16 at 18:15
Pleas read [how to make good reproducible pandas examples](http://stackoverflow.com/questions/20109391/how-to-make-good-reproducible-pandas-examples) — MaxU - stand with Ukraine, Oct 18 '16 at 18:50

pandas updating column value using isin and loc

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