Adding Columns in loop pandas

Question

I have a 2 dataframes each with 2 columns (named the same in both df's) and I want to add them together to make a third column.

df1['C']=df1[['A','B']].sum(axis=1) 
 df1['D']=df1[['E','G']].sum(axis=1)
df2['C']=df2[['A','B']].sum(axis=1) 
 df2['D']=df2[['E','G']].sum(axis=1)

However in reality its more complicated than this. So can I put these in a dictionary and loop?

I'm still figuring out how to structure dictionarys for this type of problem, so any advice would be great.

Here's what I'm trying to do:

all_dfs=[df1,df2]

for df in all_dfs:

dict={Out=['C'], in=['A','B]
    Out2=['D'], in2=['E','G]
}

for i in dict:
    df[i]=df[['i[1....

I'm a bit lost in how to build this last bit

jezrael · Accepted Answer · 2018-12-22 15:54:03Z

1

First change dictionary name because dict is python code word, then change it by key with output column and value by list of input columns and last loop by items() method:

d= {'C':['A','B'],'D': ['E','G']}

for k, v in d.items():
    #checking key and value of dict
    print (k)
    print (v) 
    df[k]=df[v].sum(axis=1)

EDIT:

Here is simplier working with dictionary of DataFrames, use sum and last create anoter dictionary of DataFrames:

all_dfs= {'first': df1, 'second':df2}
out = {}

for name, df in all_dfs.items():
    d= {'C':['A','B'],'D': ['E','G']}
    for k, v in d.items():
        df[k]=df[v].sum(axis=1)
        #fill empty dict by name
        out[name] = df

print (out)
print (out['first'])
print (out['second'])

edited Dec 22, 2018 at 15:54

answered Dec 22, 2018 at 15:22

jezrael

868k103 gold badges1.4k silver badges1.3k bronze badges

Sign up to request clarification or add additional context in comments.

10 Comments

fred.schwartz Over a year ago

This works great. I've just had another idea, can I do this to 2 dataframes as well?

fred.schwartz Over a year ago

you gave me this yesterday: all_df=[Price,RSP] Price, RSP = [d.reindex(forindex) for d in all_df]

fred.schwartz Over a year ago

Just trying to figure out how to apply this in this situation

jezrael Over a year ago

So need dictionary of DataFrames in output?

jezrael Over a year ago

@fred.schwartz - Added solution, please check it.

|

Collectives™ on Stack Overflow

Adding Columns in loop pandas

1 Answer 1

10 Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

10 Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related