Question

I want to automate the file name used when saving a spreadsheet using xlwt. Say there is a sub directory named Data in the folder the python program is running. I want the program to count the number of files in that folder (# = n). Then the filename must end in (n+1). If there are 0 files in the folder, the filename must be Trial_1.xls. This file must be saved in that sub directory.

I know the following:

import xlwt, os, os.path
n = len([name for name in os.listdir('.') if os.path.isfile(name)])

counts the number of files in the same folder.

a = n + 1
filename = "Trial_" + "a" + ".xls"
book.save(filename)

this will save the file properly named in to the same folder.

My question is how do I extend this in to a sub directory? Thanks.

Answer 1

os.listdir('.') the . in this points to the directory from where the file is executed. Change the . to point to the subdirectory you are interested in.

You should give it the full path name from the root of your file system; otherwise it will be relative to the directory from where the script is executed. This might not be what you want; especially if you need to refer to the sub directory from another program.

You also need to provide the full path to the filename variable; which would include the sub directory.

To make life easier, just set the full path to a variable and refer to it when needed.

TARGET_DIR = '/home/me/projects/data/'
n = sum(1 for f in os.listdir(TARGET_DIR) if os.path.isfile(os.path.join(TARGET_DIR, f)))
new_name = "{}Trial_{}.xls".format(TARGET_DIR,n+1)