passchecker | Simple password strength checker | Security library

Here is a suggested version that uses the error code as a return value from the function.

When you are checking whether it contains the various types of character, it will need to work regardless of what order they occur in. An easy way (although certainly there are many alternatives) is to have boolean variables that you set when you find a character of the required type. Note that i == i.lower() is not a correct test for a lower case letter, because it also evalutates True for non-letters; use i.islower() -- and similarly for upper.