Now I am happy

src/further_examples/arrays_and_strings/reverse_str.py

@@ -1,18 +1,63 @@
 #!/usr/bin/python3
-# mari von steinkirch @2013
-# steinkirch at gmail
-        
-reverse_string = lambda s: s[::-1]
+
+# Mari von Steinkirch @ 2013
+# mari.wahl9@gmail.com
+
+# Bernardo Sulzbach (mafagafo) @ 2014
+# 1449441@gmail.com
+
+# This file defines and compares four different functions that reverse a string.
+
+# timeit is used for benchmarking.
+from timeit import timeit
 
 
-def main():
-    s1 = 'abcdefg'
-    s2 = 'buffy'
-    s3 = ''
-    print(reverse_string(s1))
-    print(reverse_string(s2))
-    print(reverse_string(s3))
-                   
-if __name__ == '__main__':
-    main()
+def reverse_1(string):
+    """
+    Slowest function. Use a list and str.join to reverse the string.
+    :param string: the string to be reversed.
+    :return: a reversed string.
+    """
+    reversed_string = []
+    # Iterates from the last to the first character.
+    for i in range(len(string) - 1, -1, -1):
+        # Appends the character to the list.
+        reversed_string.append(string[i])
+    return ''.join(reversed_string)
 
+
+def reverse_2(string):
+    """
+    Same principle as reverse_1. One-liner cousin.
+    :param string: the string to be reversed.
+    :return: a reversed string.
+    """
+    return ''.join([character for character in [string[i] for i in range(len(string) - 1, -1, -1)]])
+
+
+def reverse_3(string):
+    """
+    Another one-liner. We make a list from the characters of the string and reverse it.
+    :param string: the string to be reversed.
+    :return: a reversed string.
+    """
+    return ''.join([character for character in string][::-1])
+
+# Overkill of elegance. A bit too passionate but it defines this lambda function well.
+# Simply returns the string backwards. As fast as concise.
+reverse_lambda = lambda s: s[::-1]
+
+# Import a lowercase ASCII alphabet from the string module.
+from string import ascii_lowercase
+# We define some short strings to test our functions.
+strings = (ascii_lowercase, 'buffy', 'foo', 'bar', 'SPAM')
+# We announce what we are doing.
+print(', '.join(strings), ' should appear reversed four times if all the functions are working.\n')
+print('{:<30}:'.format('Function name'), 'benchmarking result (lower is better):')
+# Iterate over a tuple of functions.
+for function in (reverse_1, reverse_2, reverse_3, reverse_lambda):
+    name = function.__name__ if function.__name__ != "<lambda>" else 'reverse_lambda'
+    # We print the function's name and its benchmark result.
+    print("{:<30}:".format(name), timeit(name + "('string')", setup='from __main__ import ' + name))
+    # We print the output so that we can check if the function is working as expected.
+    print(', '.join(map(function, strings)), '\n')