在 Python 中创建二进制只读文件时出现 FileNotFoundError

Question

I'm creating an FTP client and am attempting to download from and upload files to an FTP server.

Downloading the files work fine as I have no issues creating a write only binary file , that does not initially exist on my local computer:

if cmnd1[0] == 'get':
    f1 = open('newDownloadText.txt', 'wb')
    ftp_cl.retrbinary("RETR " + cmnd1[1], f1.write, 1024)
    f1.close()
    ftp_cl.quit()
    break

However, I am unable to upload files to the server as I cannot successfully create a new read only binary file :

elif cmnd1[0] == 'put':
    f2 = open('newUploadTest.txt', 'rb')
    ftp_cl.storbinary("STOR " + cmnd1[1], f2)
    f2.close()
    ftp_cl.quit()
    break

My code fails when I attempt to create 'newUploadTest.txt'

Traceback (most recent call last):
  File "client.py", line 29, in <module>
    f2 = open('newUploadTest.txt', 'rb')
FileNotFoundError: [Errno 2] No such file or directory: 'newUploadTest.txt'

I have seen other posts on stackoverflow with individuals creating a new read only binary files without issues using 'rb' as a parameter, not sure why mine fails every time.

Answer 1

Code:

• File must be created before reading, whereas write mode creates the file.

creating a new read only binary files

• 'rb' mode does not Create read only binary , but it reads a binary file which already exists.
• 'rb' mode opens a binary file which already exists in a read only mode. It is not creating any file.

from os.path import isfile
if my_condition:
    file = 'newUploadTest.txt'
    # Check if the file exists
    if isfile(file):
        # open binary file
        f2 = open(file, 'rb')
        # do something...
        f2.close()
    else:
        print("File doesn't exists")