You're trying to assign a function call 'nums.append(x)' which has a 'None' value to the variable 'nums'. Therefore you can't apply the 'append'-method to a None-value.
You should just apply the append-method to your list instead:
nums = 
for i in strList:
I Developed application in C# with crystal reports and created setup file in third party (Advance) Installer.When i installed my application on client system application is working but ...