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-rwxr-xr-xchallenge-147/sgreen/python/ch-1.py50
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+#!/usr/bin/env python
+
+import math
+
+
+def is_prime(number):
+ # Return true or false if the number is a prime
+ if number < 2:
+ return False
+
+ for i in range(2, int(math.sqrt(number)) + 1):
+ if number % i == 0:
+ return False
+
+ # It's a prime
+ return True
+
+
+def is_trunc_prime(number):
+ # Return true or false if the number and all it's left truncated
+ # parts is a prime. Start with the smallest figure first
+ n = str(number)
+
+ if '0' in n:
+ # A left-truncatable prime cannot contain a zero
+ return False
+
+ for i in range(len(n), 0, -1):
+ if not is_prime(int(n[i - 1:])):
+ return False
+
+ return True
+
+
+def main():
+ solutions = []
+ number = 1
+
+ # Keep increasing number by one until we have twenty truncated prime
+ # numbers
+ while len(solutions) < 20:
+ if is_trunc_prime(number):
+ solutions.append(number)
+ number += 1
+
+ print(*solutions, sep=', ')
+
+
+if __name__ == '__main__':
+ main()