On 1/4/2015 6:34 AM, flebber wrote:
In repsonse to this question: Write a program that prints the first 100 members
of the sequence 2, -3, 4, -5, 6, -7, 8.
This is my solution it works but ugly.
series = range(2,100)
# answer = [(x,(y* -1)) for x, y in series[::2]]
# print(answer)
answer = []
for item in series:
if item % 2 != 0:
answer.append(item * -1)
else:
answer.append(item)
for item in series:
if item % 2: # since result is a number, same as != 0
item *= -1
answer.append(item)
print(answer)
I know I should be better off doing this with map but cannot get it to work. I
understand also that map returns a generator so this solution should only
working in python2(correct me please if I am wrong).
In [6]: map?
Type: builtin_function_or_method
String Form:<built-in function map>
Namespace: Python builtin
Docstring:
map(function, sequence[, sequence, ...]) -> list
Just getting something wrong
list(map((lambda x: x * -1 if (x%2 != 0)), series))
In py2, map produces a list already. In any case, above is syntax error
without else clause.
map(lambda x: x * -1 if x%2 else x, series)
If you do not have a function already, a list comp is better.
[(-1*k if k%2 else k) for k in range(2, N)]
Change [] to () and you have a generator expression.
--
Terry Jan Reedy
--
https://mail.python.org/mailman/listinfo/python-list
