One 、 Data type conversion

1. Will float , String to integer

2. The integer , Convert string to floating point

3. Binary , octal , Convert hex to decimal

4. Convert decimal to binary , octal , Hexadecimal

5. Convert a string to bytes

6. Convert bytes to strings

7. take ASCII Code to string

8. Convert a string to ASCII code  

  Two 、 Conditional control statements

A:86—100,B:71—85,C:61—70,D:0—60 Enter a grade and print out the grade （ Required if...elif）