how to join items of a list in a defined manner in Python
Is this what you're looking for? You can define the df using f-strings.
mystring = "+".join([f"df['{x}']" for x in mylist])
print(mystring)
>>> df['L11_1']+df['E12_3']+df['F7_3']
mylist = ['L11_1','E12_3','F7_3']
string = "+".join([f"df['{i}']" for i in mylist])
output:
"df['L11_1']+df['E12_3']+df['F7_3']"