Filename, date

Suppose you have a program that should be run every day. It performs some important computational task or records some data and writes a log file.

With the current date, we can generate a unique file name each day. And later, these files can be sorted and accessed by the date. This is convenient.

Example program

Here is an example program. We introduce the get_filename_datetime method. We import the datetime module. In the method, we concatenate a file name based on date.today.

Note We use the txt extension, but this can be easily changed. We must convert the date.today() result into a string with str.

from datetime import date

def get_filename_datetime():
    # Use current date to get a text file name.
    return "file-" + str(date.today()) + ".txt"

# Get full path for writing.
name = get_filename_datetime()
print("NAME", name)

path = "C:\\programs\\" + name
print("PATH", path);

with open(path, "w") as f:
    # Write data to file.
    f.write("HELLO\n")
    f.write("WORLD\n")NAME file-2017-05-17.txt
PATH C:\programs\file-2017-05-17.txtHELLO
WORLD

Notes, NAME and PATH

The get_filename_datetime method returns the file name only. So we must concatenate the path to the file (in the logging directory) before using it in open().

Note Please modify the path to one that is relevant for your system. Also, a raw string literal can be used.

A summary

A random file name can be used, but this is confusing to access later. With a date in the file name, a human can easily access the desired logging data.