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/sol2.py

@@ -1,4 +1,6 @@
 """
+Problem 7: https://projecteuler.net/problem=7
+
 By listing the first six prime numbers:
 
     2, 3, 5, 7, 11, and 13
@@ -7,14 +9,15 @@ We can see that the 6th prime is 13. What is the Nth prime number?
 """
 
 
-def isprime(number):
+def isprime(number: int) -> bool:
+    """Determines whether the given number is prime or not"""
     for i in range(2, int(number ** 0.5) + 1):
         if number % i == 0:
             return False
     return True
 
 
-def solution(n):
+def solution(nth: int = 10001) -> int:
     """Returns the n-th prime number.
 
     >>> solution(6)
@@ -29,34 +32,38 @@ def solution(n):
     229
     >>> solution(100)
     541
+    >>> solution()
+    104743
     >>> solution(3.4)
     5
     >>> solution(0)
     Traceback (most recent call last):
         ...
-    ValueError: Parameter n must be greater or equal to one.
+    ValueError: Parameter nth must be greater or equal to one.
     >>> solution(-17)
     Traceback (most recent call last):
         ...
-    ValueError: Parameter n must be greater or equal to one.
+    ValueError: Parameter nth must be greater or equal to one.
     >>> solution([])
     Traceback (most recent call last):
         ...
-    TypeError: Parameter n must be int or passive of cast to int.
+    TypeError: Parameter nth must be int or passive of cast to int.
     >>> solution("asd")
     Traceback (most recent call last):
         ...
-    TypeError: Parameter n must be int or passive of cast to int.
+    TypeError: Parameter nth must be int or passive of cast to int.
     """
     try:
-        n = int(n)
+        nth = int(nth)
     except (TypeError, ValueError):
-        raise TypeError("Parameter n must be int or passive of cast to int.")
-    if n <= 0:
-        raise ValueError("Parameter n must be greater or equal to one.")
+        raise TypeError(
+            "Parameter nth must be int or passive of cast to int."
+        ) from None
+    if nth <= 0:
+        raise ValueError("Parameter nth must be greater or equal to one.")
     primes = []
     num = 2
-    while len(primes) < n:
+    while len(primes) < nth:
         if isprime(num):
             primes.append(num)
             num += 1