understanding this python code from 2014's new year challenge

Strings are iterable by default, so one can simply iterate over each element in a string:

for c in 'Hello there':
   print c

int s = 0;

for (char c: "Happy new year to you!".toCharArray())
   s += (int) c;

System.out.println(s);

1) Built-in function ord returns integer value of char.

>>> help(ord)
Help on built - in
function ord in module __builtin__:

   ord(...)
ord(c) - > integer

Return the integer ordinal of a one - character string.

2) for loops does the iteration on each char of the string 'Happy new year to you!'

>>>
for c in 'Happy new year to you':
   ...print ord(c)
   ...
   72
97
112
112
   ...

3) (ord(c) for c in 'Happy new year to you!') is a generator expression in python.

>>> result = (ord(c) for c in 'Happy new year to you!') >>>
   result.next()
72
   >>>
   result.next()
97

So the result of combining all these expression is:

>>> sum(ord(c) for c in 'Happy new year to you!')
2014

Another possible solution could be:

>>> sum(map(lambda c: ord(c), 'Happy new year to you!'))
2014

There are other kinds of comprehensions as well. The expression surrounded by naked brackets would be a list comprehensions. Example:

[char
   for char in "string"
]

This will produce a list:

['s', 't', 'r', 'i', 'n', 'g']

And "naked" braces (aka a set comprehension) produce a set:

{
   char
   for char in "string"
}

Suggestion : 2

Though there are often several possible solutions to most HackerRank challenges, I'll try and choose the most elegant and optimized solutions for code/visualization breakdowns.,I mostly use Python throughout this blog as I find it to be a clean and intuitive language that is well-suited to HackerRank challenges.,I've been going through some HackerRank challenges recently and figured I'd take a few of the more interesting challenges and do a full code breakdown with an animated visualization.,Notice that HackerRank chose to have the origin index start at 1 (e.g., 1,2,3). We adjust the queue index to 0 for teaching purposes. Check the optional final solution variant at the bottom of this article for the version that doesn't include this extra loop.

3
Too chaotic

def minimum_bribes(q):
   bribes = 0
q = [i - 1
   for i in q
]
for i, o in enumerate(q):
   cur = i

if o - cur > 2:
   print("Too chaotic")
return

for k in q[max(o - 1, 0): i]:
   if k > o:
   bribes += 1

print(bribes)

def minimum_bribes(q):
   bribes = 0
q = [i - 1
   for i in q
]
for i, o in enumerate(q):
   cur = i

if o - cur > 2:
   print("Too chaotic")
return

for k in q[max(o - 1, 0): i]:
   if k > o:
   bribes += 1

print(bribes)

def minimum_bribes(q):
   bribes = 0

for i, o in enumerate(q):
   cur = i + 1

if o - cur > 2:
   print("Too chaotic")
return

for k in q[max(o - 2, 0): i]:
   if k > o:
   bribes += 1

print(bribes)

Suggestion : 3

Python’s simple, easy-to-learn syntax can mislead Python developers – especially those who are newer to the language – into missing some of its subtleties and underestimating the power of the diverse Python language.,This can lead to gnarly problems, such as importing another library which in turns tries to import the Python Standard Library version of a module but, since you have a module with the same name, the other package mistakenly imports your version instead of the one within the Python Standard Library. This is where bad Python errors happen.,Familiarizing oneself with the key nuances of Python, such as (but by no means limited to) the moderately advanced programming problems raised in this article, will help optimize use of the language while avoiding some of its more common errors.,(Note: This article is intended for a more advanced audience than Common Mistakes of Python Programmers, which is geared more toward those who are newer to the language.)

Python allows you to specify that a function argument is optional by providing a default value for it. While this is a great feature of the language, it can lead to some confusion when the default value is mutable. For example, consider this Python function definition:

>>> def foo(bar = []): # bar is optional and defaults to[]
if not specified
   ...bar.append("baz") # but this line could be problematic, as we 'll see...
   ...
   return bar

But let’s look at what actually happens when you do this:

>>> foo()["baz"] >>>
   foo()["baz", "baz"] >>>
   foo()["baz", "baz", "baz"]

FYI, a common workaround for this is as follows:

>>> def foo(bar = None):
   ...
   if bar is None: # or
if not bar:
   ...bar = []
   ...bar.append("baz")
   ...
   return bar
      ...
      >>>
      foo()["baz"] >>>
      foo()["baz"] >>>
      foo()["baz"]

Makes sense.

>>> B.x = 2 >>>
   print A.x, B.x, C.x
1 2 1

Yup, again as expected.

>>> A.x = 3 >>>
   print A.x, B.x, C.x
3 2 3