'How to build a dataframe out of a for loop?

I got a dataframe like this one at this link: Dataframe. We got many Cities name and 4 columns for each city. What I would like to do is to extract from this Dataframe the name of 1 or more cities with all their columns i.e If I want to extract Milano and Venezia the output should be of 10 columns (5 columns for Milano and 5 columns for Venezia).

città=["Milano Linate", "Venezia Cavanis"]
estract=[]
for c in città:
    a=df.columns.get_loc(c) 
    estract.append([a,df.iloc[:,a:a+5]])
df_estract=pd.DataFrame(estract)

With these few lines of code I can get what I want, but I am struggling in bulding the new dataframe with the columns I need. Can someone help me with this?

pythonpandasdataframefor-loop


Solution 1:[1]

If you have a dataframe df like

    A  Unnamed: 2  Unnamed: 3   B  Unnamed: 5  Unnamed: 6   C  Unnamed: 8  Unnamed: 9
0   1           2           3   4           5           6   7           8           9
1  10          11          12  13          14          15  16          17          18

then this

columns = [c for i in map(df.columns.get_loc, ["A", "B"])
             for c in df.columns[i: i + 3]]
df_AB = df[columns]

gives you

    A  Unnamed: 2  Unnamed: 3   B  Unnamed: 5  Unnamed: 6
0   1           2           3   4           5           6
1  10          11          12  13          14          15

So in your case you could try:

columns = [c for i in map(df.columns.get_loc, ["Milano Linate", "Venezia Cavanis"])
             for c in df.columns[i: i + 5]]
df_estract = df[columns]

Sources

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Source: Stack Overflow

Solution Source
Solution 1 Timus

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