Re: [Tutor] Function question

[Peter O'Doherty]

On 25-03-17 11:17, Alan Gauld via Tutor wrote:


method:

print(' '.join(anotherFunction(4))


Many thanks!
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Re: [Tutor] Function question

[Peter O'Doherty]

Many thanks!

On 25-03-17 11:17, Alan Gauld via Tutor wrote:

On 25/03/17 10:01, Peter O'Doherty wrote:


def myFunc(num):
  for i in range(num):
  print(i)

print(myFunc(4))
0
1
2
3
None #why None here?

Because your function does not have an explicit return
value so Python returns its default value - None.
So the print() inside the function body prints the 0-3
values then the function terminates and returns the (default)
None to your top level print.


def myFunc(num):
  for i in range(num):
  return i

print(myFunc(4))
0 #why just 0?

Because return always returns from the function immediately.
So you call the function, it enters the loop, sees the return for the
first element and exits. The print() then prints that returned value.

The preferred method to do what I think you were expecting is to build a
list:

def anotherFunction(num):
 result = []
 for i in range(num):
result.append(i)
 return result

Which is more concisely written using a list comprehension but
that would hide the general point - that you should accumulate results
in a collection if you want to return more than a single value.

To print the result you would typically use the string.join()
method:

print(' '.join(anotherFunction(4))





//=====
// Peter O'Doherty

// http://www.peterodoherty.net
// m...@peterodoherty.net
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[Tutor] Function question

[Peter O'Doherty]

Hi,

Apologies for the very basic question but could anyone explain the 
behaviour of these two functions (in Python3.5)?


def myFunc(num):
for i in range(num):
print(i)

print(myFunc(4))
0
1
2
3
None #why None here?


def myFunc(num):
for i in range(num):
return i

print(myFunc(4))
0 #why just 0?

Many thanks,
Peter


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Re: [Tutor] Geometric sequence

[Peter O'Doherty]

To the people who kindly replied to my question: many thanks!


On 10/31/2013 06:29 PM, Danny Yoo wrote:
As an aside: It shouldn't be too bad to write a "generator" for the 
geometric series, so that we can pick out the terms on-demand.


#
>>> def geometric(base):
... x = 1
... while True:
... yield x
... x *= base
...
>>> twos = geometric(2)
#


'twos' is a representation of the geometric series; we can then pick 
out the elements one at a time:



#
>>> twos.next()
1
>>> twos.next()
2
>>> twos.next()
4
>>> twos.next()
8
>>> twos.next()
16
>>> twos.next()
32
>>> twos.next()
64
#


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[Tutor] Geometric sequence

[Peter O'Doherty]

Hi List,

I know a geometric sequence can be produced by:

series = [2**x for x in range(7)]

But I would like to curtail the sequence before the last element excedes 
a certain value. Is there a better way of doing it that the following:


for x in range(20):
series_element = 2**x
print series_element
if series_element > 60:
break
print series

Many thanks,
Peter
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Re: [Tutor] Beginner's question

[Peter O'Doherty]

Many, many thanks to all those who replied to my question. I hope the 
next time I post, it will be with something more advanced.


Judging by the volume of replies, is it fair to say that this problem 
was much too advanced for page 16 of an introductory text?


Best wishes,
Peter


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Re: [Tutor] Beginner's question

[Peter O'Doherty]

On 11/22/2012 03:17 PM, Walter Prins wrote:

Hi Peter,


On 22 November 2012 12:55, Peter O'Doherty <mailto:m...@peterodoherty.net>> wrote:


Hi list,
Firstly, apologies for the low-level nature of this question -
it's really quite basic but I don't seem to be able to solve it.

I need to write a program that examines 3 variables x, y, z, and
prints the largest odd number. I've tried all sorts of variations
and this is the current version:

x, y, z = 26, 15, 20

if x > y and x > z and x%2 != 0:
print 'x is largest and odd'
elif y > x and y > z and y%2 != 0:
print 'y is largest and odd'
elif z > x and z > y and z%2 != 0:
print 'z is largest and odd'
else:
print 'no odd'


The key logical mistake you make is that by your current logic the 
*smallest* number can never be the largest odd number, which is 
obviously false as in your example.


Break the problem down (divide and conquer).  Suppose I gave you only 
2 numbers, and you had to say which of the 2 numbers were the largest 
odd, what would be the possible outcomes and what would the the 
solution be?  (Hint, both can be odd, only x can be odd, only y can be 
odd, or neither can be odd.)   Once you have that answer, then repeat 
the exact same solution for the first 2 numbers and apply to the 
answer from x&y and and the remaining z.  The result from that is 
tells you the largest odd number from all 3. (Aside, your question 
states to print the largest odd number, which I interpret to mean the 
value, not the name of the variable holding the value.  )


Walter


Thanks Walter.

This code appears to work although it's very cumbersome. Is there a 
better way to do it?


x, y, z = 6, 23, 16

if x%2 != 0 and y%2 !=0:
if x > y:
ans = x
else:
ans = y
elif x%2 !=0 and y%2 == 0:
ans = x
else:
ans = y

if ans%2 != 0 and z%2 !=0:
if ans > z:
ans = ans
else:
ans = z
elif ans%2 !=0 and z%2 == 0:
ans = ans
else:
    ans = z
print str(ans) + ' is largest odd'

Regards,
Peter


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//=
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-> http://www.peterodoherty.net
-> m...@peterodoherty.net
-> https://joindiaspora.com/people/70716
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Re: [Tutor] Beginner's question

[Peter O'Doherty]

Hi Varun,

Thanks for your reply.
I agree the problem is logic - but how can one inspect one number using 
if x%2 == 0 and then compare it to two other numbers which should at the 
same time be checked for "oddness", just using the basic constructs?


Thanks,
Peter


On 11/22/2012 02:06 PM, Varun Nagpal wrote:

Hi Peter,

The reason why your program is not behaving as it should is not 
Pythonic but rather logic.


Instead of giving away the code, I would suggest you revisit the 'and' 
conditions.


The program should print the largest odd number i.e. the number which 
is largest among all odd numbers.

Instead you are printing the number which is largest AND odd.

--
Varun


On Thu, Nov 22, 2012 at 6:25 PM, Peter O'Doherty 
mailto:m...@peterodoherty.net>> wrote:


Hi list,
Firstly, apologies for the low-level nature of this question -
it's really quite basic but I don't seem to be able to solve it.

I need to write a program that examines 3 variables x, y, z, and
prints the largest odd number. I've tried all sorts of variations
and this is the current version:

x, y, z = 26, 15, 20

if x > y and x > z and x%2 != 0:
print 'x is largest and odd'
elif y > x and y > z and y%2 != 0:
print 'y is largest and odd'
elif z > x and z > y and z%2 != 0:
print 'z is largest and odd'
else:
print 'no odd'


A solution should be possible using only the simple operators and
keywords above, no functions, lists or any other form of
iteration. (It's from p. 16 of Introduction to Computation and
Programming Using Python, and no, it's not "homework"!)

Many thanks,
Peter



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-> http://www.peterodoherty.net
-> m...@peterodoherty.net
-> https://joindiaspora.com/people/70716
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[Tutor] Beginner's question

[Peter O'Doherty]

Hi list,
Firstly, apologies for the low-level nature of this question - it's 
really quite basic but I don't seem to be able to solve it.


I need to write a program that examines 3 variables x, y, z, and prints 
the largest odd number. I've tried all sorts of variations and this is 
the current version:


x, y, z = 26, 15, 20

if x > y and x > z and x%2 != 0:
print 'x is largest and odd'
elif y > x and y > z and y%2 != 0:
print 'y is largest and odd'
elif z > x and z > y and z%2 != 0:
print 'z is largest and odd'
else:
print 'no odd'


A solution should be possible using only the simple operators and 
keywords above, no functions, lists or any other form of iteration. 
(It's from p. 16 of Introduction to Computation and Programming Using 
Python, and no, it's not "homework"!)


Many thanks,
Peter



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