[Tutor] Off-Topic: Tutor group specific to Java
Hello Guys, This is kind of off-topic, but I would really appreciate it if anyone could provide me with a tutor mailing list/group specific to Java. I am a beginner, and it would be really helpful for me. -- Thanks & Regards, Karthik A Bhat ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: https://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Defining variable arguments in a function in python
Thank you all for the quick response!
On Sun, Dec 30, 2018 at 10:39 AM Avi Gross wrote:
> I have my usual off the wall answer.
>
> OK, seriously. Not exactly an answer but perhaps an experiment.
>
> The question was how to have a non-named first argument to a function with
> some form of default.
>
> As was pointed out, this does not fit well with being able to have python
> gather all positional arguments after it as well as all keyword arguments.
>
> But bear with me. Say I want to have a way to signal that I want a default
> for the first argument?
>
> An empty comma fails but try this:
>
> def hello(a, *n, **m) :
> if a == None: a=5
> print(a)
> print(*n)
> print(**m)
>
> The above says "a" is required. It can be followed by any number of
> positional args gathered into "n" and any number of keyword args gathered
> into "m"
>
> But what if you define a sentinel to watch for such as None, in the above?
>
> If the first and only arg is None, it switches to the default of 5.
>
> >>> hello(None)
> 5
>
> Add a few more args and it properly takes it.
>
> >>> hello(1,2,3)
> 1
> 2 3
>
> Switch the first to None:
>
> >>> hello(None,2,3)
> 5
> 2 3
>
> The keywords don't work for print but no biggie.
>
> But is this only for None? What I say any negative arg is replaced by 5?
>
> def hello(a, *n, **m) :
> if a < 0: a=5
> print(a)
> print(*n)
>
> Seems to work fine:
>
> >>> hello(-666, 2, 3, 4)
> 5
> 2 3 4
>
> And I wonder if we can use the darn ellipsis for something useful?
>
> def hello(a, *n, **m) :
> if a == ... : a=5
> print(a)
> print(*n)
>
> >>> hello(1,2,3)
> 1
> 2 3
> >>> hello(...,2,3)
> 5
> 2 3
> >>> hello(...,2,...)
> 5
> 2 Ellipsis
>
> OK, all kidding aside, is this helpful? I mean if you want a function where
> you MUST give at least one arg and specify the first arg can be some odd
> choice (as above) and then be replaced by a default perhaps it would be
> tolerable to use None or an Ellipsis.
>
> Or on a more practical level, say a function wants an input from 1 to 10.
> The if statement above can be something like:
>
> >>> def hello(a, *n, **m) :
> if not (1 <= a <= 10) : a=5
> print(a)
> print(*n)
>
>
> >>> hello(1,2,3)
> 1
> 2 3
> >>> hello(21,2,3)
> 5
> 2 3
> >>> hello(-5,2,3)
> 5
> 2 3
> >>> hello("infinity and beyond",2,3)
> Traceback (most recent call last):
> File "", line 1, in
> hello("infinity and beyond",2,3)
> File "", line 2, in hello
> if not (1 <= a <= 10) : a=5
> TypeError: '<=' not supported between instances of 'int' and 'str'
>
> As expected, it may take a bit more code such as checking if you got an int
> but the idea may be solid enough. It is NOT the same as having a default
> from the command line but it may satisfy some need.
>
> Other than that, I fully agree that the current python spec cannot support
> anything like this in the function definition.
>
> Side note: To spare others, I sent Steven alone a deeper reply about ways
> to
> select random rows from a pandas DataFrame. I am still learning how pandas
> works and doubt many others here have any immediate needs.
>
>
>
>
>
>
>
>
>
> -Original Message-
> From: Tutor On Behalf Of
> Steven D'Aprano
> Sent: Saturday, December 29, 2018 6:02 AM
> To: tutor@python.org
> Subject: Re: [Tutor] Defining variable arguments in a function in python
>
> On Sat, Dec 29, 2018 at 11:42:16AM +0530, Karthik Bhat wrote:
> > Hello,
> >
> > I have the following piece of code. In this, I wanted to make
> > use of the optional parameter given to 'a', i.e- '5', and not '1'
> >
> > def fun_varargs(a=5, *numbers, **dict):
> [...]
> >
> > fun_varargs(1,2,3,4,5,6,7,8,9,10,Jack=111,John=222,Jimmy=333)
> >
> > How do I make the tuple 'number' contain the first element to be 1 and
> not
> 2?
>
>
> You can't. Python allocates positional arguments like "a" first, and only
> then collects whatever is left over in *numbers. How else would you expect
> it to work? Suppose you called:
>
> fun_varargs(1, 2, 3)
>
> wanting a to get the value 1, and numbers to get the values (2, 3). And
> then
> immediately after that you call
>
> fun_varargs(1, 2, 3)
>
> wanting a to g
[Tutor] Defining variable arguments in a function in python
Hello,
I have the following piece of code. In this, I wanted to make use
of the optional parameter given to 'a', i.e- '5', and not '1'
def fun_varargs(a=5, *numbers, **dict):
print("Value of a is",a)
for i in numbers:
print("Value of i is",i)
for i, j in dict.items():
print("The value of i and j are:",i,j)
fun_varargs(1,2,3,4,5,6,7,8,9,10,Jack=111,John=222,Jimmy=333)
How do I make the tuple 'number' contain the first element to be 1 and not
2?
--
Regards,
Karthik A Bhat
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[Tutor] Facebook apps with python
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[Tutor] Memory error - how to manage large data sets?
Hi, I am new to Python programming, I was trying to work out a few problems in order to grasp the knowledge gained after going through the basic chapters on Python programming. I got stuck with a memory error. Following is what I did, 1. I need to find the sum of all numbers at even positions in the Fibonacci series upto 2 million. 2. I have used lists to achieve this. 3. My program works good with smaller ranges. Say till 10,000 or even 100,000. However when I compute the sum for bigger ranges it gives me the memory error. 4. Also could someone tell me how to get the result in the form of an exponent. For instance, I would prefer 10^5 rather 10. Thanks in advance, Karthik ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Memory error - how to manage large data sets?
Forgot to include the following information, Platform - win32 Version - 2.5.1 Error message: Traceback (most recent call last): File C:\Python25\programs\fibo.py, line 10, in module if i % 2 == 0: MemoryError Code: fib = [] even = [] def fibonacci(x,y): return x+y for i in range (0,100): if i 2: fib.append(i) else: i = fib[i-1] + fib[i-2] if i % 2 == 0: fib.append(i) even.append(i) else: fib.append(i) total = reduce(fibonacci,even) print total Any pointers would be of great help to me. Regards, Karthik From: Karthik [mailto:[EMAIL PROTECTED] Sent: Monday, July 28, 2008 9:27 PM To: 'tutor@python.org' Subject: Memory error - how to manage large data sets? Hi, I am new to Python programming, I was trying to work out a few problems in order to grasp the knowledge gained after going through the basic chapters on Python programming. I got stuck with a memory error. Following is what I did, 1. I need to find the sum of all numbers at even positions in the Fibonacci series upto 2 million. 2. I have used lists to achieve this. 3. My program works good with smaller ranges. Say till 10,000 or even 100,000. However when I compute the sum for bigger ranges it gives me the memory error. 4. Also could someone tell me how to get the result in the form of an exponent. For instance, I would prefer 10^5 rather 10. Thanks in advance, Karthik ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
