Add default args and type hints for problem 7 (#2973)

- Add default argument values
- Add type hints
- Change one letter variable names to a more descriptive one
- Add doctest for `solution()`

project_euler/problem_07/sol3.py

@@ -1,4 +1,6 @@
 """
+Project 7: https://projecteuler.net/problem=7
+
 By listing the first six prime numbers:
 
     2, 3, 5, 7, 11, and 13
@@ -9,7 +11,8 @@ import itertools
 import math
 
 
-def primeCheck(number):
+def prime_check(number: int) -> bool:
+    """Determines whether a given number is prime or not"""
     if number % 2 == 0 and number > 2:
         return False
     return all(number % i for i in range(3, int(math.sqrt(number)) + 1, 2))
@@ -18,12 +21,12 @@ def primeCheck(number):
 def prime_generator():
     num = 2
     while True:
-        if primeCheck(num):
+        if prime_check(num):
             yield num
         num += 1
 
 
-def solution(n):
+def solution(nth: int = 10001) -> int:
     """Returns the n-th prime number.
 
     >>> solution(6)
@@ -38,8 +41,10 @@ def solution(n):
     229
     >>> solution(100)
     541
+    >>> solution()
+    104743
     """
-    return next(itertools.islice(prime_generator(), n - 1, n))
+    return next(itertools.islice(prime_generator(), nth - 1, nth))
 
 
 if __name__ == "__main__":