python - 在 Python 中，如何确定对象是否可迭代？

Question

有没有类似isiterable的方法？到目前为止我找到的唯一解决方案是调用

hasattr(myObj, '__iter__')

但我不确定这是多么简单。

Answer 1

1. 检查 __iter__ 适用于序列类型，但会失败，例如Python 2 中的字符串。我也想知道正确的答案，在那之前，这是一种可能性(也适用于字符串):

    try:
        some_object_iterator = iter(some_object)
    except TypeError as te:
        print(some_object, 'is not iterable')
   

iter 内置检查 __iter__ 方法，如果是字符串，则检查 __getitem__ 方法。

1. 另一种通用的pythonic方法是假设一个可迭代的，然后如果它不适用于给定的对象，则优雅地失败。 Python 词汇表:

Pythonic programming style that determines an object's type by inspection of its method or attribute signature rather than by explicit relationship to some type object ("If it looks like a duck and quacks like a duck, it must be a duck.") By emphasizing interfaces rather than specific types, well-designed code improves its flexibility by allowing polymorphic substitution. Duck-typing avoids tests using type() or isinstance(). Instead, it typically employs the EAFP (Easier to Ask Forgiveness than Permission) style of programming.

...

try:
   _ = (e for e in my_object)
except TypeError:
   print my_object, 'is not iterable'

1. collections模块提供了一些抽象基类，允许询问类或实例是否提供特定功能，例如:

    from collections.abc import Iterable
   
    if isinstance(e, Iterable):
        # e is iterable
   

但是，这不会检查可通过 __getitem__ 迭代的类。