logger.error("HostedService associator should NOT return excepted result with a wrong key name and value of %s input" % k)

The above log stmt would not fit in the 80 columns in a single line and hence we would require the stmt to be continued on the next line, we can do it using the \ as below:

logger.error("HostedService associator should NOT return excepted result with \
a wrong key name and value of %s input" % k)

But in case you do not want to use the \ you can write the above in the following way

logger.error("HostedService associator should NOT return excepted result with "
             "a wrong key name and value of %s input" % k)

The same thing applies if the element of the list does not accommodate in a single line within 80 columns.

For ex:

expr_values = { "invalid_ccname" : {"rc"  : pywbem.CIM_ERR_NOT_FOUND, 
                                    "desc": "No such instance "\
(CreationClassName)"}}

For ex above we do not need a \ after the value pywbem.CIM_ERR_NOT_FOUND of rc key in the list. But we would require a \ to complete the value "No such instance (CreationClassName)"
of the key desc above.
Again, as in the logger stmt we can write the above without the \ as follows:

expr_values = { "invalid_ccname" : {  "rc" : pywbem.CIM_ERR_NOT_FOUND,
                                    "desc" : "No such instance "
                                           "(CreationClassName)"}}

The rule of using \ applies almost like in the C language, for ex in the pre processor stmts we make use of the \ if we are not able to complete the stmt in a single line.
But we dont use it in case of function parameters distributed over 2 different lines.

Hope this helps.

Thanks and Regards,
Deepti.