How to use the iter() function in Python to obtain the iterator of an iterable object

How to use the iter() function in Python to obtain the iterator of an iterable object

In Python, iteration is a very common programming operation. Through iteration operations, we can access the elements in an iterable object one by one. Iterable objects in Python include lists, tuples, strings, dictionaries, sets, etc. To implement iterative operations, we first need to obtain the iterator of the iterable object. The iter() function is used to obtain the iterator of an iterable object.

The iter() function is a built-in function in Python that returns an iterator object. An iterator is an object that can access elements one by one through the next() function. The iter() function has two main uses, namely passing in an iterable object and a callable object.

First, let’s look at the first usage, which is to pass in an iterable object. The following is an example:

num_list = [1, 2, 3, 4, 5]
iter_obj = iter(num_list)

print(next(iter_obj))  # 输出1
print(next(iter_obj))  # 输出2
print(next(iter_obj))  # 输出3
print(next(iter_obj))  # 输出4
print(next(iter_obj))  # 输出5

In this example, we first define a list num_list, and then convert it into an iterator object iter_obj# through the iter() function ##. After that, we use the next() function to access the elements in iter_obj one by one, and the output results are 1, 2, 3, 4, and 5.

It should be noted that when the iterator reaches the end of the iterable object, calling the next() function again will throw a StopIteration exception. Therefore, when using the next() function, we need to perform exception handling to ensure that no errors will occur after the iteration is completed.

Another usage is to pass in a callable object. Callable objects refer to objects that can be called like functions, such as functions, class objects, etc. By passing a callable object to the iter() function, we can create an iterator that iterates infinitely. Here is an example:

import random

class RandomNumberGenerator:
    def __iter__(self):
        return self

    def __next__(self):
        return random.randint(1, 10)

rng = RandomNumberGenerator()
iter_obj = iter(rng)

print(next(iter_obj))  # 输出一个随机数
print(next(iter_obj))  # 输出另一个随机数
print(next(iter_obj))  # 又输出一个随机数

In this example, we define a

RandomNumberGenerator class that implements __iter__() and __next__() method. The __iter__() method returns self, the iterator object itself, while the __next__() method returns a random number each time it is called. Then, we created a RandomNumberGenerator objectrng and passed it into the iter() function to obtain the iterator object iter_obj. Finally, we use the next() function to access the elements in iter_obj one by one, and the output result is a randomly generated value.

In summary, the iter() function is a very convenient function in Python for obtaining the iterator of an iterable object. Through the iter() function, we can convert various iterable objects into iterators to achieve the operation of accessing elements one by one. When using the iter() function, we need to pay attention to exception handling to ensure that no errors occur after the iteration is completed. Whether an iterable object or a callable object is passed in, the iter() function can return the corresponding iterator object, and the elements in the iterator can be accessed through the next() function.

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