Question

I’m trying to read a list of items from a text file and format with square brackets and separators like this: [‘item1′,’item2’, …. ‘last_item’] but I’m having trouble with the beginning and end item for which I always get: …,’last_item’,’], so I do not want the last ,’ to be there.

In python I’ve write:

out_list = "['"
for line in open(file_in):  
    out_list += line                #append the item to the list
    out_accession_list += "','"     #add the separator
out_accession_list += "]"           #add the final closed bracket
return out_list                        

I realize that this is a basic loop question, but I can’t think of the best way to do it. Should I use a try final statement, should it be a while loop, or should I count the number of lines first and then use a loop with a range?

Help much appreciated.

Thanks,
John

Answer 1

Read in all your lines and use the string.join() method to join them together.

lines = open(file_in).readlines()

out_list = "['" + "','".join(lines) + "']"

Additionally, join() can take any sequence, so reading the lines isn’t necessary. The above code can be simplified as:

out_list = "['" + "','".join(open(file_in)) + "']"