Knowledge Learning python

** indicates deep calculation
// represents division rounding
\ represents escape
r "" can be used to avoid escape

• For the string attached to
  the string * copy number indicates the number of string
  variables [0] represents the variable in the first one, [1] for the first two
  variables [-1] represents a variable in the penultimate one, [ -2] is the inverse of the second
  endsWith () expressed in xx end
  startsWith () represented by xxx beginning
  isdigit () if string contains only numeric was True, otherwise to False
  len () returns the string length
  lower () converts characters string in all uppercase letters to lowercase
  replacement string the replace (Old, new new)
  rstrip () delete the end of the string of blanks
  upper () converts a string of lowercase to uppercase
  append () to add list items
  list.append () end of the list add a new object
  list.sort () to sort the list
  list.clear () Clear list