[Tutor] all right students, what do we learn

Clayton Kirkwood crk at godblessthe.us
Sun Nov 2 06:43:43 CET 2014

```To prove that a little knowledge is a little stupid or something to that
effect:

#    for key in key_list:

#        print(key)

#        if key not in key_list0:

#            print("Error:", key, "not available, start again")

#            get_new_list = True

#            break

#    else: get_new_list = False

Assume key_list0 = [('a', 'Ask'), ('y', 'Dividend Yield')]

The above worked when key_list was 'a y' or 'hhh'

Well, if a little cool was good why not use all of my new found knowledge of
comprehensions.

So I head down the path of all sorts of variations of the following. And I
mean all sorts. Instead of [reenter, key_columns] I used a single list.
Instead of the exec('reenter = True') I used a simple reenter=True (and an
eval and compile which I don't totally understand yet). Turns out that
python doesn't seem to like an assignment in the overall if clause - error.
Weird thing, entering   a y   would make the final print spit out (False,
'a') (False, 'o') but the entry of  hhh   caused the final print to spit out
[] (in the best of the various experiments. Which I don't quite understand.
The reason is because I set up the if statement to be True either way. With
an   a   it would go thru and create the proper output. But with  hhh   the
print prints out the Error:.., and I was hoping the assignment of True to
reenter would create a  True  which would make it out to the while. But it
won't. I think I have to just stay with the more verbose as above. Besides
after trying so many variations the comprehension was getting rather
kluge:<))

But  really grok comprehension a lot better.

reenter=True

while reenter:

reenter=False

key_list = input('Please enter space separated keys in the order you
want: ').split()

[reenter, key_columns ]=[(reenter, key) for key in key_list if ((key in
key_list0)) or (print("Error:", key, "not available, start again") and
exec('reenter = True', ))]

print(reenter,key_columns)

Clayton

You can tell the caliber of a man by his gun--c. kirkwood

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