Python 中的无限迭代器
原文:https://www.geeksforgeeks.org/infinite-iterators-in-python/
Python 中的迭代器是可以与“for in loop”一起使用的任何 Python 类型。Python 列表、元组、字典和集合都是内置迭代器的例子。但是迭代器对象不必用尽，有时它可以是无限的。这种迭代器被称为无限迭代器。
Python 提供了三种类型的无限迭代器–
-
count(start, step): This iterator starts printing from the “start” number and prints infinitely. If steps are mentioned, the numbers are skipped else step is 1 by default. See the below example for its use with
for inloop.示例:
```py
Python program to demonstrate
infinite iterators
import itertools
for in loop
for i in itertools.count(5, 5): if i == 35: break else: print(i, end =" ") ```
输出:
```py 5 10 15 20 25 30
```
-
cycle(iterable): This iterator prints all values in order from the passed container. It restarts printing from beginning again when all elements are printed in a cyclic manner.
示例#1:
```py
Python program to demonstrate
infinite iterators
import itertools
count = 0
for in loop
for i in itertools.cycle('AB'): if count > 7: break else: print(i, end = " ") count += 1 ```
输出:
```py A B A B A B A B
```
示例#2: 使用下一个函数。
```py
Python program to demonstrate
infinite iterators
import itertools
l = ['Geeks', 'for', 'Geeks']
defining iterator
iterators = itertools.cycle(l)
for in loop
for i in range(6):
# Using next function print(next(iterators), end = " ") ```
输出:
```py Geeks for Geeks Geeks for Geeks
```
-
repeat(val, num): This iterator repeatedly prints the passed value infinite number of times. If the optional keyword
numis mentioned, then it repeatedly printsnumnumber of times.示例:
```py
Python code to demonstrate the working of
repeat()
importing "itertools" for iterator operations
import itertools
using repeat() to repeatedly print number
print ("Printing the numbers repeatedly : ") print (list(itertools.repeat(25, 4))) ```
输出:
```py Printing the numbers repeatedly : [25, 25, 25, 25]
```
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