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  OK, let's continue.

  • Conditional Judgments and Loop
    • if
    • if-else
    • if-elif-else
    • while
    • for
    • break
    • continue
    • multiple loop


  • Differences between Dict and Set
    • Dict: A kind of structure in the type of "Key-Value"
      • described in "{}"
      • formed by "key: value"
      • function "len()" to calculate the length
      • judge empty:① if 'key' in dict  ②dict.get('key')  ->if empty, return None automatically
      • the key in dict is unchangeable
    • Set: A kind of struture in the type of Non-repeating elements collection
      • described in "set([,,,,])" 
      • add() to add elements
      • remove() to delete elements
  • Functions

        A function can return single value, as well as return more value. But in essence it returns one, a tuple. The function treats the values as a tuple.

1 >>> r = move(100, 100, 60, math.pi / 6)
2 >>> print r
3 (151.96152422706632, 70.0)
    • recursive functions:  take care of overflowing
    • default parameter: set default parameter in the function line in the blankets, and the default parameter must be set at the right side 
    • variable parameter: use '*' to mark variable parameter , and they are regarded as a tuple