Project Euler Problem 10: style improvements (#2924)

Rename the main solution functions to solution.
Rename prime chec functions to is_prime.
Add default args, typehints, expand variable names.

project_euler/problem_10/sol1.py

@@ -1,4 +1,6 @@
 """
+https://projecteuler.net/problem=10
+
 Problem Statement:
 The sum of the primes below 10 is 2 + 3 + 5 + 7 = 17.
 
@@ -7,7 +9,17 @@ Find the sum of all the primes below two million.
 from math import sqrt
 
 
-def is_prime(n):
+def is_prime(n: int) -> bool:
+    """Returns boolean representing primality of given number num.
+    >>> is_prime(2)
+    True
+    >>> is_prime(3)
+    True
+    >>> is_prime(27)
+    False
+    >>> is_prime(2999)
+    True
+    """
     for i in range(2, int(sqrt(n)) + 1):
         if n % i == 0:
             return False
@@ -15,20 +27,7 @@ def is_prime(n):
     return True
 
 
-def sum_of_primes(n):
-    if n > 2:
-        sumOfPrimes = 2
-    else:
-        return 0
-
-    for i in range(3, n, 2):
-        if is_prime(i):
-            sumOfPrimes += i
-
-    return sumOfPrimes
-
-
-def solution(n):
+def solution(n: int = 2000000) -> int:
     """Returns the sum of all the primes below n.
 
     # The code below has been commented due to slow execution affecting Travis.
@@ -43,7 +42,16 @@ def solution(n):
     >>> solution(7)
     10
     """
-    return sum_of_primes(n)
+    if n > 2:
+        sum_of_primes = 2
+    else:
+        return 0
+
+    for i in range(3, n, 2):
+        if is_prime(i):
+            sum_of_primes += i
+
+    return sum_of_primes
 
 
 if __name__ == "__main__":