What does the in keyword mean in a Python for loop?

The most commonly used cases, I understand, such as

 for I inch Range (1,5):    Print I

Reply content:

Keywords: iterators

In simple terms, the for in statement is a syntactic sugar, specifically:

• Calling an object's __iter__ method, the method returns an iterator that is the object that implements the __next__ method, and if an object itself implements the __next__ (a direct "next" method in Python 2, without an underscore), it can return itself directly.
• The __next__ of the call iterator returns the "next" element in the iterator, for example, the first call returns 0, and the second returns 1, and so on.
• There is no element at the end, and the iterator throws an exception to indicate that it has no elements. The For statement catches the exception and stops.

I suggest you write a Fibonacci iterator on your own.
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In addition, there is a ecstasy called the generator, demonstrating how gracefully Fibonacci:
(Since then the code for brevity I have written in Python, with Python 2 can run but poor performance.) ）

deffib(n):   a=0   b=1   for_inrange(n):       a,b=b,a+b       yielda

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This for is actually an iteration, using an iterator (Iterator).

# 以下代码在Python 2中运行for row in f: print row# 完全等价于itr = f.__iter__() # 获得新的迭代器while True: try: row = itr.next() except StopIteration: break print row

Iterators.

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Discovery is Get_iter, For_iter and the like. Discovery is Get_iter, For_iter and the like this is the range (1:5) and F as a container to see. Since there is a line in the file F, the row is naturally a string. As a personal understanding:
inchKeyword implements a set of traversal protocols in Python.

• Protocol A: __iter__ + next
  

Loop, the program uses __iter__ (equivalent to ITER (instance)) to obtain an object with the next method, and then, through its returned object, calls its next method continuously until Stopiteration error thrown.

class A:    def __iter__( Self):         Self.Limit = 4         Self. Times = 0         Self.Init = 1        return  Self    def Next( Self):        if  Self. Times >=  Self.Limit:            Raise stopiteration()        Else:            x =  Self.Init             Self. Times += 1             Self.Init += 1            return xPrint ' a>>>>>> ' for x inch A():    Print x

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