1. Write a Python program to check whether a string represent an integer or not.
Example:
Please enter a string: Python # this is user input
This is not an integer.
2. Write a Python function to remove the character of index n from a non empty string.
3. Write a Python program which prompts the user to create a user account and checks whether the provided user name and password are legal.
Note: a user name should start with a letter and only consists of letters and numbers. The length should be between 6 and 12; a password should start with a letter and only consists of letters, numbers of the underscore symbol "_". The length should be between 8 to 16.
4. Write a Python function to get the first half of a specified string of even length. Suppose the input string is "Python", after calling the function, we should see the output "Pyt".