On Sun, Dec 01, 2013 at 08:43:46AM -0500, bruce wrote:
> hmm...
>
> two questions. (new to cmdline py)
>
> tried typing in what was typed in above in the python shell:
>
> for i in range(1, 101):
> print "2" in str(i)
>
> this did nothing..
Curious. Which Python shell did you use?
I would expect that you get a prompt ">>>" (without the quotes). I've
changed the prompt in my Python to "py>", but by default you should have
">>>". Then, when you hit return at the end of the first line, you
should get the second level prompt, "...". You'll need to add at least
one space, or tab, to indent the second line. Then when you hit enter
again you'll get a ... prompt, Enter one last time and the code will
run. Here's what I get (changing 101 to a smaller number for brevity:
py> for i in range(1, 11):
... "2" in str(i)
...
False
True
False
False
False
False
False
False
False
False
However, I may have inadvertently been misleading. Outside of the
interactive shell, even though that code will run, it won't display any
output. Only in the interactive shell does that print True and False as
above.
Outside of the interactive shell, you need to use the print statement or
function to see the output, otherwise Python calculates the answer and
then doesn't do anything with it. So it may be better to write this as:
for i in range(1, 101):
print ("2" in str(i))
which will work anywhere.
> def aa():
> for i in range(1, 101):
> print "2" in str(i)
>
> aa()
>
> error::
> >>> aa()
> Traceback (most recent call last):
> File "<stdin>", line 1, in <module>
> NameError: name 'aa' is not defined
That is remarkable. I cannot explain this error. Are you using IDLE or
some other shell?
> the other question, what does the "in" function within py do?? I've
> used str.find() to look if a substring is present, but didn't know a
> "in" even exists..!
The "in" operator tests whether one object includes another object. For
example, with strings it tests substrings:
"hat" in "what"
=> returns True
"hat" in "h-a-t"
=> returns False
With lists and tuples, it tests to see if an item is the given value:
23 in [1, 5, 23, 99]
=> returns True
"dog" in ["cat", "dog", "mouse"]
=> returns True
"dog" in ["cats", "dogs", "mice"]
=> return False
But it only looks one level deep!
23 in [1, 2, 3, [22, 23, 24], 5, 6]
=> returns False
With dictionaries, it checks to see if the given object is a key:
5 in {2: "two", 5: "five", 7: "seven"} # {key: value}
=> returns True
but not a value:
"five" in {2: "two", 5: "five", 7: "seven"}
=> returns False
--
Steven
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