当我阅读发电机教程https://realpython.com/introduction-to-python-generators/时会出现此问题。 is_palindrome(101)
返回True,但是代码未打印101。我调试并看到yield 101
将执行返回到主for
循环,该循环立即返回到生成器,这非常令人困惑。生成器的产量为101,因此应该为for j in pal_gen:
的元素,不是吗?
def is_palindrome(num):
# Skip single-digit inputs
if num // 10 == 0:
return False
temp = num
reversed_num = 0
while temp != 0:
reversed_num = (reversed_num * 10) + (temp % 10)
temp = temp // 10
if num == reversed_num:
return True
else:
return False
def infinite_palindromes():
num = 0
while True:
if is_palindrome(num):
i = (yield num)
if i is not None:
num = i
num += 1
if __name__=='__main__':
pal_gen = infinite_palindromes()
for j in pal_gen:
print(f'j={j}')
digits = len(str(j))
if digits == 5:
pal_gen.close()
pal_gen.send(10 ** (digits))
当前输出为:
j=11
j=111
j=1111
j=10101
Traceback (most recent call last):
File "generator.py", line 33, in <module>
pal_gen.send(10 ** (digits))
StopIteration
您会注意到它在每个之间都跳过了一个。缺少101,缺少1001。缺少10001。我很确定send
使生成器运行到下一个yield语句。例如,使用以下代码:
if __name__=='__main__':
pal_gen = infinite_palindromes()
for j in pal_gen:
print('j={}'.format(j))
digits = len(str(j))
if digits == 5:
pal_gen.close()
print(pal_gen.send(10 ** (digits)))
这将打印出“ j”之间的缺失值:
j=11
101
j=111
1001
j=1111
10001
j=10101
考虑使用for
重做while
语句:
if __name__=='__main__':
pal_gen = infinite_palindromes()
j=next(pal_gen)
digits=0
while digits<5:
print('j={}'.format(j))
digits = len(str(j))
j = pal_gen.send(10 ** (digits))
else:
pal_gen.close()