枚举'for' function

Question

I want to add a column named X in every .tsv file. I want this column to have the value of the corresponding index in the folder_names list (one value of the folder_names per.tsv file). But the enumerate function repeat itself in each iteration of the for loop , so the column 'X' always get the last value of names instead of the corresponding one.

I got these two lists:

all_files_tsv = [tsv_file_1, tsv_file_2.... tsv_file_n]

folder_names = [folder_name_1, folder_name_2.... folder_name_n]

And the output desired is the following:

tsv_file_1 :

Column1	Column2	X
1	A	folder_name_1
2	B	folder_name_1
3	C	folder_name_1

tsv_file_2 :

Column1	Column2	X
1	---	folder_name_2
2	---	folder_name_2
3	---	folder_name_2

And this is the code that I have right now:

for file_ in all_files_tsv:
    df = pd.read_csv(file_,sep = '\t', header=0)
    for index, names in enumerate(folder_names):
        df['X'] = names

Any idea of how could I solve this?

Answer 1

You don't need enumerate() . You can iterate over all_files_tsv and folder_names in parallel using zip() to get corresponding elements.

for file, name in zip(all_files_tsv, folder_names):
    df = pd.read_csv(file, sep='\t', header=0)
    df['X'] = name
    df.to_csv(file, sep='\t', header=0)

Nested loops are used when you want a cross product between two lists, zip() is used when you want to pair corresponding elements.