Re: [Tutor] need help with conditionals
On Sep 26, 2009, at 11:42 PM, Alan Gauld wrote: "Kent Johnson" wrote It appears to be http://openbookproject.net/thinkCSpy/ch04.html So it is, Thats a shame CSpy is one of my favourite "competitors" :-) Pity it's apparently encouraging the use of eval like this with no caveat. But to the OP, keep with it, its not a bad tutorial, shame about this exercise! Perhaps worth alerting the author? He's a nice guy and i e-mailed him many moons ago when i was working through that book with some concerns i had. He was really receptive and grateful to get feed back and was quick to make changes if he thought they would improv the text. A super good dude and it seems, a top notch educator. He tends to credit *everyone* who sends in a suggestion, no matter how minor. ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] need help with conditionals
On Sat, Sep 26, 2009 at 3:59 AM, Alan Gauld wrote: > What are you using for a tutorial? It appears to be http://openbookproject.net/thinkCSpy/ch04.html Kent ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] need help with conditionals
"Kent Johnson" wrote It appears to be http://openbookproject.net/thinkCSpy/ch04.html So it is, Thats a shame CSpy is one of my favourite "competitors" :-) Pity it's apparently encouraging the use of eval like this with no caveat. But to the OP, keep with it, its not a bad tutorial, shame about this exercise! -- Alan Gauld Author of the Learn to Program web site http://www.alan-g.me.uk/ ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] need help with conditionals
wrote
been really frustrating me. Here's a copy of the problem, and sorry if
its really
long but its the end question about the logically equivalent expressions
I'm
stuck on. Anyways, heres a copy of the problem
First send us the real code you have used not a copy of your homework.
And secondly send us the complete error message not a summary.
Python error messages are extremely helpful once you learn how
to read them.
Then we might be able to help.
As Corey said my tutorial contains some stuff on understanding
booleans, but the most useful section for truth tables is in the
Functional Programming topic in the Advanced section.
But this question actually has nothing to do with conditionals
or booleans! :-)
The following Python script prints out the truth table for the any
boolean
expression in two variables: p and q:
expression = raw_input("Enter a boolean expression in two variables, p
and q: ")
print " p q %s" % expression
length = len( " p q %s" % expression)
print length*"="
for p in True, False:
for q in True, False:
print "%-7s %-7s %-7s" % (p, q, eval(expression))
You will learn how this script works in later chapters. For now, you will
use it to
learn about boolean expressions. Copy this program to a file named
p_and_q.py,
Thats a terrible name BTW it would be better to call it truthtable.py!
from p_and_q import *
And this is bad practice!
What are you using for a tutorial?
If its not for a class I would consider finding another...
Use the truth_table functions with the following boolean expressions,
recording
the truth table produced each time:
not(p or q)
not(p and q)
not(p) or not(q)
not(p) and not(q)
Also show us a cut n pasdte of you running the program - so we can see
what you are typing as input. Using eval() like this is very prone to user
error
and also considered bad practice!
HTH,
--
Alan Gauld
Author of the Learn to Program web site
http://www.alan-g.me.uk/
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Re: [Tutor] need help with conditionals
wrobl...@cmich.edu wrote:
Hello all,
I am still very new to Python and am working on conditionals. Im stuck on this
problem and I'm sorry if this is something really simple that I'm missing but its
been really frustrating me. Here's a copy of the problem, and sorry if its really
long but its the end question about the logically equivalent expressions I'm
stuck on. Anyways, heres a copy of the problem
it works for me...
"""
Python 2.6.1 (r261:67517, Dec 4 2008, 16:51:00) [MSC v.1500 32 bit
(Intel)] on
win32
Type "help", "copyright", "credits" or "license" for more information.
>>> def truth_table(expression):
... print " p q %s" % expression
... length = len( " p q %s" % expression)
... print length*"="
... for p in True, False:
... for q in True, False:
... print "%-7s %-7s %-7s" % (p, q, eval(expression))
...
>>> truth_table("p or q")
p q p or q
=
TrueTrueTrue
TrueFalse True
False TrueTrue
False False False
>>> truth_table("not(p) and not(q)")
p q not(p) and not(q)
TrueTrueFalse
TrueFalse False
False TrueFalse
False False True
>>> truth_table("not(p or q)")
p q not(p or q)
==
TrueTrueFalse
TrueFalse False
False TrueFalse
False False True
>>> truth_table("p and q")
p q p and q
==
TrueTrueTrue
TrueFalse False
False TrueFalse
False False False
"""
How are you calling the truth_table()?
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Re: [Tutor] need help with conditionals
> Hello all,
> I am still very new to Python and am working on conditionals. Im stuck
on this
> problem and I'm sorry if this is something really simple that I'm
missing but its
> been really frustrating me. Here's a copy of the problem, and sorry if
its really
> long but its the end question about the logically equivalent expressions
I'm
> stuck on. Anyways, heres a copy of the problem
>
> ---
>
> >>> from p_and_q import *
> >>> truth_table("p or q")
Are you calling the function as shown above?
>
> Whenever I try to enter the expressions listed into the prompt it tells
me the
> string object is not callable
It would be helpful if you showed us exactly what you type into the prompt
and the exact error you get. You should be calling the function as it is
shown in the problem.
Assuming the function is entered and imported correctly you should get a
true table output.
two examples:
>>> truth_table("p or q")
p q p or q
=
TrueTrueTrue
TrueFalse True
False TrueTrue
False False False
>>> truth_table("not(p or q)")
p q not(p or q)
==
TrueTrueFalse
TrueFalse False
False TrueFalse
False False True
Without a bit more info its hard to guess what is happening.
Chris___
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