如何将变量用作目录？在FTP代码中用log_dir定位文件上传

Hey Matt, great questions—let's walk through how to solve this cleanly and reliably.

First: How to Use a Variable as a Directory Path #

The key here is to dynamically build your file path using safe, cross-platform methods instead of hardcoding or manually string-concatenating paths (which breaks easily across Windows/macOS/Linux).

Python gives you two solid options for this:

• The traditional os.path module
• The modern pathlib library (Python 3.4+, highly recommended for readability)

Applying This to Your FTP Code #

Since your key_log.txt is in the same directory as your script, setting log_dir = "" will work perfectly with either method—they'll default to the current working directory.

Option 1: Using os.path.join() #

This method handles path separators (\ on Windows, / on Unix-like systems) automatically, so you don't have to worry about typos or system differences.

import os
import ftplib

# Your directory variable (empty = current directory)
log_dir = ""

# Build the full path to your log file
file_path = os.path.join(log_dir, "key_log.txt")

# Open the file and upload via FTP (using a `with` statement to auto-close the file)
with open(file_path, 'rb') as fh:
    ftp = ftplib.FTP("your-ftp-server.com")
    ftp.login("your-username", "your-password")
    ftp.storbinary("STOR key_log.txt", fh)  # "STOR" tells FTP to store the file
    ftp.quit()

Option 2: Using pathlib (Modern Approach) #

pathlib uses object-oriented syntax, making path operations more intuitive. The / operator acts as a path separator—super clean!

from pathlib import Path
import ftplib

log_dir = ""

# Build the path (empty log_dir means current directory)
file_path = Path(log_dir) / "key_log.txt"

# Use pathlib's built-in open method (still with `with` for safety)
with file_path.open('rb') as fh:
    ftp = ftplib.FTP("your-ftp-server.com")
    ftp.login("your-username", "your-password")
    ftp.storbinary("STOR key_log.txt", fh)
    ftp.quit()

Bonus: Handling Non-Existent Directories #

If you ever change log_dir to a directory that doesn't exist yet (e.g., log_dir = "./archive/logs"), you can add a line to create the directory automatically:

• For os.path:

  os.makedirs(os.path.dirname(file_path), exist_ok=True)
  

• For pathlib:

  file_path.parent.mkdir(parents=True, exist_ok=True)
  

The exist_ok=True flag prevents errors if the directory already exists.

内容的提问来源于stack exchange，提问作者Matt J