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I am trying to save a pandas dataframe column instance. but the instance disappears once I make an update in that column, I can't get access to the old instance anymore. 

C= DF.loc[:,'10']
print(C)
DF.loc[:,'10'] = None
print(C)

In the first print I get the last instance of DF.loc[:,'10'], in the second one I get a None column. How should I do to save the old instance to use it later? Does python make an update on variables of the dataframe even when I already saved it? Thanks for helping.

petezurich
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echtouka
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1 Answers1

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In python, setting a variable actually sets a reference to the variable. Variable names in python are references to the original.

The following code should make a copy of C and store in D

C= DF.loc[:,'10']
print(C)
D= DF.loc[:,'10'].copy()

DF.loc[:,'10'] = None
print(C)
Irfanuddin
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  • can you please explain the phenomen why does python updates on variables? Thank you – echtouka Oct 01 '18 at 16:12
  • @echtouka That is because in python setting a variable actually sets a reference to the variable. Variable names in python are references to the original. I would recommend you to read the answer in [this](https://stackoverflow.com/questions/2612802/how-to-clone-or-copy-a-list) – Irfanuddin Oct 01 '18 at 16:38