【1】
li=list(string(a))
NameError: name 'string' is not defined
Python int与string之间的转化
https://www.cnblogs.com/nzbbody/p/3581048.html
str(18)
list(s ) 将序列 s 转换为一个列表
python中的字符数字之间的转换函数
http://www.cnblogs.com/wuxiangli/p/6046800.html
【2】字符串反转reverse函数
http://www.cnblogs.com/wuxiangli/p/6046800.html
Backwards Read Primes are primes that when read backwards in base 10 (from right to left) are a different prime. (This rules out primes which are palindromes.)
向后读素数是指在基数10（从右到左）向后读时是不同素数的素数。（这排除了作为回文的素数。）
Examples: 13 17 31 37 71 73 are Backwards Read Primes
13 is such because it's prime and read from right to left writes 31 which is prime too. Same for the others.
Example
backwardsPrime(2, 100) => [13, 17, 31, 37, 71, 73, 79, 97] backwardsPrime(9900, 10000) => [9923, 9931, 9941, 9967] backwardsPrime(501, 599) => []
Find all Backwards Read Primes between two positive given numbers (both inclusive), the second one always being greater than or equal to the first one. The resulting array or the resulting string will be ordered following the natural order of the prime
找出两个正的给定数字（都包含）之间的所有向后读素数，第二个总是大于或等于第一个。结果数组或结果字符串的顺序将遵循素数的自然顺序
实现代码如下：
def backwardsPrime(start, stop):
a=[]
for val in range(start, stop):
if is_prime(val) and is_prime(f1(val)):
a.append(val)
return a
def f1(a):
li=list(str(a))
li.reverse()
a2=''.join(li)
return int(a2)
def is_prime(num):
k=0
if num>1:
for i in range(1,num):
if num%i==0:
k+=1
else:
continue
if k==1:
return True
else:
return False
测试通过，但是提交代码报错
为什么我的代码超时？
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解锁解决方案（遗失资格）
range和xrange的区别
https://blog.csdn.net/jayandchuxu/article/details/54897887
python3没有了xrange
https://blog.csdn.net/mvs2008/article/details/73693012
别人的代码:
def prime(a):
if a == 2: return True
if a < 2 or a % 2 == 0: return False
return not any(a % x == 0 for x in range(3, int(a**0.5) + 1, 2))
def backwardsPrime(start, nd):
return [x for x in range(start, nd + 1) if (str(x) != str(x)[::-1]) and prime(x) and prime(int(str(x)[::-1])) ]