From e9e4e5f5729c81d6a1b03fe91d00d00ec0df261b Mon Sep 17 00:00:00 2001
From: shellhub <shellhub.me@gmail.com>
Date: Thu, 31 Oct 2019 18:57:11 +0800
Subject: [PATCH 1/2] update factorial

---
 maths/factorial_python.py    | 15 +++++++++------
 maths/factorial_recursive.py | 21 +++++++++++++++------
 2 files changed, 24 insertions(+), 12 deletions(-)

diff --git a/maths/factorial_python.py b/maths/factorial_python.py
index ab97cd41e681..91accfdb5d44 100644
--- a/maths/factorial_python.py
+++ b/maths/factorial_python.py
@@ -12,10 +12,13 @@ def factorial(input_number: int) -> int:
 
     if input_number < 0:
         raise ValueError("Input input_number should be non-negative")
-    elif input_number == 0:
-        return 1
-    else:
-        result = 1
-        for i in range(input_number):
-            result = result * (i + 1)
+    result = 1
+    for i in range(1, input_number):
+        result = result * (i + 1)
     return result
+
+
+if __name__ == '__main__':
+    import doctest
+
+    doctest.testmod()
\ No newline at end of file
diff --git a/maths/factorial_recursive.py b/maths/factorial_recursive.py
index f346c65f1962..4026f093af36 100644
--- a/maths/factorial_recursive.py
+++ b/maths/factorial_recursive.py
@@ -1,14 +1,23 @@
-def fact(n):
+def factorial(n):
     """
-    Return 1, if n is 1 or below,
+    Return 1, if n is 1 or 0,
     otherwise, return n * fact(n-1).
+
+    >>> factorial(1)
+    1
+    >>> factorial(6)
+    720
+    >>> factorial(0)
+    1
     """
-    return 1 if n <= 1 else n * fact(n - 1)
+    if n < 0:
+        raise ValueError(n, "is negative")
+    return 1 if n == 0 or n == 1 else n * factorial(n - 1)
 
 
 """
 Show factorial for i,
-where i ranges from 1 to 20.
+where i ranges from 0 to 20.
 """
-for i in range(1, 21):
-    print(i, ": ", fact(i), sep="")
+for i in range(21):
+    print(i, ": ", factorial(i), sep="")

From d5470a10a328f3a3f6f9dc46123bfd4dd5e07271 Mon Sep 17 00:00:00 2001
From: shellhub <shellhub.me@gmail.com>
Date: Thu, 31 Oct 2019 20:24:19 +0800
Subject: [PATCH 2/2] update factorial

---
 maths/factorial_python.py    | 30 ++++++++++++++++++++----------
 maths/factorial_recursive.py | 27 +++++++++++++++++----------
 2 files changed, 37 insertions(+), 20 deletions(-)

diff --git a/maths/factorial_python.py b/maths/factorial_python.py
index 91accfdb5d44..b9adfdbaeaff 100644
--- a/maths/factorial_python.py
+++ b/maths/factorial_python.py
@@ -1,17 +1,27 @@
 def factorial(input_number: int) -> int:
     """
-        Non-recursive algorithm of finding factorial of the
-        input number.
-        >>> factorial(1)
-        1
-        >>> factorial(6)
-        720
-        >>> factorial(0)
-        1
+    Calculate the factorial of specified number
+
+    >>> factorial(1)
+    1
+    >>> factorial(6)
+    720
+    >>> factorial(0)
+    1
+    >>> factorial(-1)
+    Traceback (most recent call last):
+        ...
+    ValueError: factorial() not defined for negative values
+    >>> factorial(0.1)
+    Traceback (most recent call last):
+        ...
+    ValueError: factorial() only accepts integral values
     """
 
     if input_number < 0:
-        raise ValueError("Input input_number should be non-negative")
+        raise ValueError("factorial() not defined for negative values")
+    if not isinstance(input_number, int):
+        raise ValueError("factorial() only accepts integral values")
     result = 1
     for i in range(1, input_number):
         result = result * (i + 1)
@@ -21,4 +31,4 @@ def factorial(input_number: int) -> int:
 if __name__ == '__main__':
     import doctest
 
-    doctest.testmod()
\ No newline at end of file
+    doctest.testmod()
diff --git a/maths/factorial_recursive.py b/maths/factorial_recursive.py
index 4026f093af36..013560b28b42 100644
--- a/maths/factorial_recursive.py
+++ b/maths/factorial_recursive.py
@@ -1,7 +1,6 @@
-def factorial(n):
+def factorial(n: int) -> int:
     """
-    Return 1, if n is 1 or 0,
-    otherwise, return n * fact(n-1).
+    Calculate the factorial of specified number
 
     >>> factorial(1)
     1
@@ -9,15 +8,23 @@ def factorial(n):
     720
     >>> factorial(0)
     1
+    >>> factorial(-1)
+    Traceback (most recent call last):
+        ...
+    ValueError: factorial() not defined for negative values
+    >>> factorial(0.1)
+    Traceback (most recent call last):
+        ...
+    ValueError: factorial() only accepts integral values
     """
     if n < 0:
-        raise ValueError(n, "is negative")
+        raise ValueError("factorial() not defined for negative values")
+    if not isinstance(n, int):
+        raise ValueError("factorial() only accepts integral values")
     return 1 if n == 0 or n == 1 else n * factorial(n - 1)
 
 
-"""
-Show factorial for i,
-where i ranges from 0 to 20.
-"""
-for i in range(21):
-    print(i, ": ", factorial(i), sep="")
+if __name__ == '__main__':
+    import doctest
+
+    doctest.testmod()