How to understand python iterable objects

What is an iterable object?

The simple understanding is that objects that can be used for loops are iterable objects. For example: list, string, dict, tuple, generator, etc.

Have iterable characteristics. (Recommended learning: Python video tutorial)

Custom iterable object (essence)

At the syntax level, if an object implements __iter__ method, then this object is an iterable object

Judge whether it is an iterable object (Iterable)

通过调用Python内置的isinstance来判断是否是Iterable的实例

In [9]: isinstance([],Iterable)
Out[9]: True

In [10]: isinstance('',Iterable)
Out[10]: True

In [11]: isinstance({},Iterable)
Out[11]: True

In [12]: class MyList(object):
....:     def __init__(self):
....:         self.list = []
....:     def add(self,item):
....:         self.list.append(item)
....:         

In [13]: mylist = MyList()

In [14]: isinstance(mylist,Iterable)
Out[14]: False

Through the above example It can be seen that the objects of the built-in types dict, list, and str in Python are all iterable. We have customized a class MyList. Since this class does not implement the iter method, instances of this class are not iterable objects.

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