我正在练习发电机，我想知道为什么下面的代码不能打印16对但只有4对。
WIN32_FIND_DATAW输出
FindClose虽然我期望的输出是
def range_generator_function(my_range):
for i in my_range:
yield i
gen1=range_generator_function(range(1,5))
gen2=range_generator_function(range(1,5))
def pairs_generator_function(gen1,gen2):
for it1 in gen1:
for it2 in gen2:
yield [it1,it2]
my_gen = pairs_generator_function(gen1,gen2)
for it in my_gen:
print(it)
答案 0 :(得分：5)
实际输出是正确的。您的gen2实例已被第一个内循环完全耗尽：
def pairs_generator_function(gen1,gen2):
for it1 in gen1:
for it2 in gen2: # <--- this consumes gen2
yield [it1,it2]
在随后的迭代中，再次迭代gen2为空。
答案 1 :(得分：2)
第一次通过内循环后，你耗尽了gen2。您不再拥有该流中的任何内容，因此gen2的其他三个值与配对无关。您需要每次都重新启动itertools.tee。考虑 <section
id="em_widget-6" class="widget widget_em_widget"><ul><li
class="haekken-event"><a
href="https://www.haekken.de/events/pale-seas/" class="event-link"><div
class="event-info"><div><h2><span>Pale Seas – verlegt!</span></h2><p
class="event-meta">09_März | <span
style="text-transform: uppercase;">Live</span></p></div></div><img
src="https://www.haekken.de/wp-content/uploads/PALE-SEAS-_online.jpg" alt="Event-Foto"/></a></li><li
class="haekken-event"><a
href="https://www.haekken.de/events/banfi/" class="event-link"><div
class="event-info"><div><h2><span>Banfi</span></h2><p
class="event-meta">13_März | <span
style="text-transform: uppercase;">Live</span></p></div></div><img
src="https://www.haekken.de/wp-content/uploads/banfi_press_online.jpg" alt="Event-Foto"/></a></li><li
class="haekken-event"><a
href="https://www.haekken.de/events/2908/" class="event-link"><div
class="event-info"><div><h2><span>Kiez Treats – Binkbeats</span></h2><p
class="event-meta">15_März | <span
style="text-transform: uppercase;">Live</span></p></div></div><img
src="https://www.haekken.de/wp-content/uploads/binkbeats_press_online.jpg" alt="Event-Foto"/></a></li><li
class="haekken-event"><a
href="https://www.haekken.de/events/mynth/" class="event-link"><div
class="event-info"><div><h2><span>Mynth</span></h2><p
class="event-meta">16_März | <span
style="text-transform: uppercase;">Live</span></p></div></div><img
src="https://www.haekken.de/wp-content/uploads/de-0419-826366-back.jpg" alt="Event-Foto"/></a></li><li
class="haekken-event"><a
href="https://www.haekken.de/events/noah-gundersen/" class="event-link"><div
class="event-info"><div><h2><span>Noah Gundersen</span></h2><p
class="event-meta">17_März | <span
style="text-transform: uppercase;">Live</span></p></div></div><img
src="https://www.haekken.de/wp-content/uploads/noah_gundersen_online.jpg" alt="Event-Foto"/></a></li><li
class="haekken-event"><a
href="https://www.haekken.de/events/garden-city-movement/" class="event-link"><div
class="event-info"><div><h2><span>Garden City Movement – verlegt!!!</span></h2><p
class="event-meta">19_März | <span
style="text-transform: uppercase;">Live</span></p></div></div><img
src="https://www.haekken.de/wp-content/uploads/Garden-City-Movement_online.jpg" alt="Event-Foto"/></a></li><li
class="haekken-event"><a
href="https://www.haekken.de/events/trails/" class="event-link"><div
class="event-info"><div><h2><span>Trails</span></h2><p
class="event-meta">21_März | <span
style="text-transform: uppercase;">Live</span></p></div></div><img
src="https://www.haekken.de/wp-content/uploads/TRAILS_online.jpg" alt="Event-Foto"/></a></li><li
class="haekken-event"><a
href="https://www.haekken.de/events/james-chatburn-wayne-snow/" class="event-link"><div
class="event-info"><div><h2><span>James Chatburn & Wayne Snow</span></h2><p
class="event-meta">22_März | <span
style="text-transform: uppercase;">Live</span></p></div></div><img
src="https://www.haekken.de/wp-content/uploads/chatburn_snow_online.jpg" alt="Event-Foto"/></a></li><li
class="haekken-event"><a
href="https://www.haekken.de/events/amy-shark/" class="event-link"><div
class="event-info"><div><h2><span>Amy Shark – AUSVERKAUFT!</span></h2><p
class="event-meta">26_März | <span
style="text-transform: uppercase;">Live</span></p></div></div><img
src="https://www.haekken.de/wp-content/uploads/AmyShark_Pressshot12018_online.jpg" alt="Event-Foto"/></a></li><li
class="haekken-event"><a
href="https://www.haekken.de/events/hippie-sabotage/" class="event-link"><div
class="event-info"><div><h2><span>Hippie Sabotage</span></h2><p
class="event-meta">27_März | <span
style="text-transform: uppercase;">Live</span></p></div></div><img
src="https://www.haekken.de/wp-content/uploads/Hippiesabotage_online.jpg" alt="Event-Foto"/></a></li><li
class="haekken-event"><a
href="https://www.haekken.de/events/me-reas/" class="event-link"><div
class="event-info"><div><h2><span>Me & Reas</span></h2><p
class="event-meta">28_März | <span
style="text-transform: uppercase;">Live</span></p></div></div><img
src="https://www.haekken.de/wp-content/uploads/Me-Reas_1_©-David-Häuser_online.jpg" alt="Event-Foto"/></a></li><li
class="haekken-event"><a
href="https://www.haekken.de/events/projectbeatmaker-spring-session/" class="event-link"><div
class="event-info"><div><h2><span>Project:Beatmaker – Spring Session</span></h2><p
class="event-meta">30_März | <span
style="text-transform: uppercase;">Club</span></p></div></div><img
src="https://www.haekken.de/wp-content/uploads/projectbeatmaker_logo.png" alt="Event-Foto"/></a></li><li
class="haekken-event"><a
href="https://www.haekken.de/events/kiez-treats-peter-broderick/" class="event-link"><div
class="event-info"><div><h2><span>Kiez Treats – Peter Broderick</span></h2><p
class="event-meta">12_April | <span
style="text-transform: uppercase;">Live</span></p></div></div><img
src="https://www.haekken.de/wp-content/uploads/Peter-7-by-Declan-Kelly_online.jpg" alt="Event-Foto"/></a></li><li
class="haekken-event"><a
href="https://www.haekken.de/events/holly-miranda/" class="event-link"><div
class="event-info"><div><h2><span>Holly Miranda</span></h2><p
class="event-meta">13_April | <span
style="text-transform: uppercase;">Live</span></p></div></div><img
src="https://www.haekken.de/wp-content/uploads/holly-miranda-750_0.jpg" alt="Event-Foto"/></a></li><li
class="haekken-event"><a
href="https://www.haekken.de/events/glode/" class="event-link"><div
class="event-info"><div><h2><span>Gløde</span></h2><p
class="event-meta">14_April | <span
style="text-transform: uppercase;">Live</span></p></div></div><img
src="https://www.haekken.de/wp-content/uploads/BY-JULIEN-FERTL2_online.jpg" alt="Event-Foto"/></a></li><li
class="haekken-event"><a
href="https://www.haekken.de/events/this-is-the-kit/" class="event-link"><div
class="event-info"><div><h2><span>This Is The Kit</span></h2><p
class="event-meta">20_April | <span
style="text-transform: uppercase;">Live</span></p></div></div><img
src="https://www.haekken.de/wp-content/uploads/thisisthekit_online.jpg" alt="Event-Foto"/></a></li><li
class="haekken-event"><a
href="https://www.haekken.de/events/marvin-brooks/" class="event-link"><div
class="event-info"><div><h2><span>Marvin Brooks</span></h2><p
class="event-meta">21_April | <span
style="text-transform: uppercase;">Live</span></p></div></div><img
src="https://www.haekken.de/wp-content/uploads/Marvin-Brooks1_NICULAI_CONSTANTINESCU_PHOTOGRAPY_online.jpg" alt="Event-Foto"/></a></li><li
class="haekken-event">
克隆更多副本。
答案 2 :(得分：1)
您获得的输出是由于在第二次迭代中，生成器gen2已用尽。
您可以在循环之前使用list来存储其输出，或者在每次迭代时使用itertools.tee复制它。前者无法处理无限生成器，但在实现后者之前，让我指出您实际上正在重新实现itertools.product。
from itertools import product
my_gen = product(gen1, gen2)
for it in my_gen:
print(it)
答案 3 :(得分：0)
我修改了代码以便获得所需的输出，现在每次在外部循环中重新创建生成器。
def range_generator_function(my_range):
for i in my_range:
yield i
def pairs_generator_function():
gen1=range_generator_function(range(1,5))
for it1 in gen1:
gen2=range_generator_function(range(1,5))
for it2 in gen2:
yield [it1,it2]
my_gen = pairs_generator_function()
for it in my_gen:
print(it)
答案 4 :(得分：0)
正如@wim指出的那样，在第一次迭代后你的生成器完全耗尽了。但是，为了防止这种情况，请将gen2和pairs_generator_function作为列表传递给itertools.tee。但是，您可以使用import itertools
def range_generator_function(my_range):
for i in my_range:
yield i
gen1=range_generator_function(range(1,5))
gen2=range_generator_function(range(1,5))
def pairs_generator_function(gen1,gen2):
for it1 in gen1:
for it2 in gen2:
yield [it1,it2]
gen1, gen1_l = itertools.tee(gen1)
gen2, gen2_l = itertools.tee(gen2)
print(list(pairs_generator_function(list(gen1_l), list(gen2_l))))
存储原始生成器的两个副本：一个用于作为列表传递给函数，另一个用于将来使用：
[[1, 1], [1, 2], [1, 3], [1, 4], [2, 1], [2, 2], [2, 3], [2, 4], [3, 1], [3, 2], [3, 3], [3, 4], [4, 1], [4, 2], [4, 3], [4, 4]]
输出：
gen1但请注意，>>next(gen1)
1
>>next(gen2)
1
和gen2`仍然指向内存中的项目：
public abstract class EO {
@Autowired
protected SmsNotificationService smsNotificationService;
@Autowired
protected SendEmailService sendEmailService;
...
protected abstract void executeOperation(GenericMessage gMessage);
}
public final class OperationsExecutor {
public enum OperationsType {
ENROLL, CAMPAIGN
}
private OperationsExecutor() {
}
public static Object delegateOperation(OperationsType type, Object obj)
{
switch(type) {
case ENROLL:
if (obj == null) {
return new EnrollOperation();
}
return EnrollOperation.validateRequestParams(obj);
case CAMPAIGN:
if (obj == null) {
return new CampaignOperation();
}
return CampaignOperation.validateRequestParams(obj);
default:
throw new IllegalArgumentException("OperationsType not supported.");
}
}
}
@Configurable(dependencyCheck = true)
public class CampaignOperation extends EO {
@Override
public void executeOperation(GenericMessage genericMessage) {
LOGGER.info("This is CAMPAIGN Operation: " + genericMessage);
}
}