deleting list element if the element is present on another column of a dataframe-CodePudding

I have a list of dataframe list=[df1,df2,df3,df4,...df10] the dataframe are constructed as following :

>df1
     col1  col2  col3  col4
      Y     2     XX     PP

I have another dataframe DATA_SEL such that

>DATA_SEL
col1  col2  col3  col4
A      KK   C      D
A1     PP   C      D
...................
..................

If the first value (a string) of col4 for every dataframe in list (df1 ,df2,df3....df10 )does not match with any value of col2 in DATA_SEL , I want to delete that df from list. How could I possibly do that?

Also if I want to construct a new list, list2 where the first value (a string) of col4 for every dataframe in list (df1 ,df2,df3....df10 ) matches with any value of col2 in DATA_SEL , how to do that?

CodePudding user response：

Use list comprehension with filtering:

L = [df1,df2,df3,df4,...df10]

#tested first value of col4
out = [x for x in L if DATA_SEL['col2'].eq(x.at[x.index[0], 'col4']).any()]
#if first row has index == 0
out = [x for x in L if DATA_SEL['col2'].eq(x.at[0, 'col4']).any()]

#tested any value of col4
out = [x for x in L if DATA_SEL['col2'].isin(x['col4']).any()]