Python生成日志路径触发TypeError: not all arguments converted报错求助

Hey there! Let's break down what's causing this error and fix it quickly.

The Root Cause #

Your line:

log_file_path = os.path.join(log_dir, 'Params.txt' % datetime.strftime(datetime.today(), '%Y%m%d'))

is throwing an error because you're using the string formatting operator % on the string 'Params.txt'—but this string has no placeholder (like %s) where Python can insert the formatted date string. Python sees you're passing a value to format with, but nowhere to put it, hence the TypeError.

You want to append the date to your log filename (like Params_20240520.txt), right? Here are a few clean ways to do that:

Solution 1: Use F-Strings (Recommended for Python 3.6+) #

F-strings are the most readable and concise way to format strings now:

from datetime import datetime
import os

log_dir = os.path.abspath(os.path.join(__file__, "../../", 'logs'))
# Embed the formatted date directly in the filename string
log_file_path = os.path.join(log_dir, f'Params_{datetime.today().strftime("%Y%m%d")}.txt')

Solution 2: String Concatenation #

If you prefer a more explicit approach, build the filename by concatenating strings:

from datetime import datetime
import os

log_dir = os.path.abspath(os.path.join(__file__, "../../", 'logs'))
date_str = datetime.today().strftime("%Y%m%d")
log_file_path = os.path.join(log_dir, 'Params_' + date_str + '.txt')

Solution 3: Use the .format() Method #

For older Python versions (pre-3.6), the .format() method works reliably:

from datetime import datetime
import os

log_dir = os.path.abspath(os.path.join(__file__, "../../", 'logs'))
date_str = datetime.today().strftime("%Y%m%d")
log_file_path = os.path.join(log_dir, 'Params_{}.txt'.format(date_str))

All these approaches will generate a filename like Params_20240520.txt (with today's date) and avoid the formatting error you ran into.

内容的提问来源于stack exchange，提问作者J.Doe