Now it's time to work on the next custom module called SSH connection dot p y. This module contains three sections. The first section checks if the text file containing the username and password, which are the login credentials for our Arista switches exists on the local file system. The second part of the module verifies whether the text file containing all the commands to be sent to each device exists on the local system. And finally, the central piece of the module is the SSH connection function, which performs all the hard work of connecting to each switch sending the commands and storing the output. However, more on that in the following lectures.

For now, let's focus on the file storing the login credentials. The verification process is very similar to the one we used for checking the existence of the text file holding the IP addresses. So first of all, we are asking the user to Input the name of the file holding the username and password, including the full path and extension of that file. To make things crystal clear, we are providing an example in between parentheses right here, the input will be stored as a string using the user file variable. Next, using the East file method from within OS dot path, we are checking whether the file exists on the local file system or not. And if this turns out to be true, we print out a confirmation message to the screen.

Otherwise, we told the user that the file does not exist and then exit the program allowing him or her to check the file or the path. At this point. If the file is verified and validated, we can move on to the next verification