Mailman 3 September 2011 - Python-ideas

return value of yield expressions
by H. Krishnan Sept. 16, 2011

Sept. 16, 2011

Hi, I should start off by saying that my knowledge of PEP342 is less than a week old, and I cannot claim any use-case for what I am about to propose. The PEP itself says "In effect, a yield-expression is like an inverted function call; the argument to yield is in fact returned (yielded) from the currently executing function, and the "return value" of yield is the argument passed in via send()." One could, I guess, wrap a function to be 'called' via this mechanism: def genwrap(func): def … [View More]

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Object interface to path names
by David Townshend Sept. 16, 2011

Sept. 16, 2011

I've recently been developing a tool to track changes to a fairly large structured file system, and in the process got to thinking about how working with path names could be improved. The problems I've had with using just os and os.path have lead to three objectives of any new implementation: 1. Cleaner handling of paths names, specifically constructing path names without the need for a lot of nested os.path.join() and os.split() functions. 2. Allow a validation of paths names based on … [View More]

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threading : AttributeError: 'NoneType' object has no attribute 'start'
by Sagar Neve Sept. 14, 2011

Sept. 14, 2011

I am new to the python and I need a small script to be written using threads which reads the specific files present in a directory and does some selections of lines and then write those lines into different files. However the error I am getting is: AttributeError: 'NoneType' object has no attribute 'start' Here is the code. Can somebody please help me. This is very urgent. def getFiles(fname): fname=preprocessLogFileDir + "/" + fname print fname fin = open(fname, "r") … [View More]

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List Revolution
by Christopher King Sept. 12, 2011

Sept. 12, 2011

The first element in a list is element zero, the second is one, the third it two, and so on. This some times confuses newbies to the language or programming in general. This system was invited when single bits where precious. It's time to update. Keep in mind this is something for version 4, since its not reverse compatible. I say we make the first element 1, second 2, third 3, and so on. Other languages would follow. We are python, made for easiness and readability, and we are in the age where … [View More]

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Re: [Python-ideas] List Revolution
by Matt Billenstein Sept. 12, 2011

Sept. 12, 2011

Ugh, I hate the idea of library code having to think about dealing with the possibility that you chose 42 as the starting index for some list you passed into a function in said library. Then I suppose we'll have to extend this to strings and tuples and so forth as well? Seriously, any further "solutions" for this non-problem are just mental masturbation -- please stop. m On Sun, Sep 11, 2011 at 11:05:28PM -0700, mike.w.meyer(a)gmail.com wrote: > Ok, how about enhancing the list type to … [View More]

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Re: [Python-ideas] List Revolution
by Massimo Di Pierro Sept. 11, 2011

Sept. 11, 2011

Here is my proposal which hopefully would settle the issue to rest class List(list): """ >>> a=List() >>&… [View More]gt; for i in range(100000): a.append(i) >>> print a.first 0 >>> print a.second 1 >>> print a.third 2 >>> print a.twentieth 19 >>> print a.twentysecond 21 >>> print a.onehundredthirtyfifth 134 >>> print a.onethousandfivehundredandthirtyeighth 1537 """ def __getattr__(self,name): import re if name.endswith('first'): name = name[:-5]+'one' elif name.endswith('second'): name = name[:-6]+'two' elif name.endswith('third'): name = name[:-5]+'three' elif name.endswith('fth'): name = name[:-3]+'ve' elif name.endswith('hth'): name = name[:-3]+'th' elif name.endswith('ieth'): name = name[:-4]+'y' elif name.endswith('th'): name = name[:-2] subs = { 'one':'+1', 'two':'+2', 'three':'+3', 'four':'+4', 'five':'+5', 'six':'+6', 'seven':'+7', 'eigth':'+8', 'nine':'+9', 'ten':'+10', 'eleven':'+11', 'twelve':'+12', 'thirteen':'+13', 'fourteen':'+14', 'fiftheen':'+15', 'sixteen':'+16', 'seventeen':'+17', 'eighteen':'+18', 'nineteen':'+19', 'ten':'+10', 'twenty':'+20', 'thirty':'+30', 'fourty':'+40', 'fifthy':'+50', 'sixty':'+60', 'seventy':'+70', 'eighty':'+80', 'ninety':'+90', 'hundred':')*100+(', 'thousand':')*1000+(', 'million':')*1000000+(', 'billion':')*1000000000+(', 'trillion':')*100000000000+(', 'and',''} for key,value in subs.items(): name = name.replace(key,value) if '(' in name: name='('+name+')' name.replace('()','1') if not re.compile('[\d\+\*\(\)]+').match(name): return AttributeError try: return self[eval(name)-1] except: raise AttributeError I would like to stress that the use of eval in this case is safe as the expression is first validated against a regex. Massimo [View Less]

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Columns for pprint.PrettyPrinter
by Julian Berman Sept. 11, 2011

Sept. 11, 2011

For the most part I find pprint to be lovely. Simple and does a useful thing that I don't want to have to write every time, especially if I'm using it just to debug. However, I often find that I'm using it to print out a long-length singly nested structure whose elements' reprs are not really that long, for which its output is cumbersome. Try to pprint.pprint(range(100)). Instead of seeing a long really skinny column, it'd be nice if it could quickly provide a way (combined with the width arg … [View More]

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relaxing keyword usage restrictions
by H Krishnan Sept. 11, 2011

Sept. 11, 2011

Hi, Apologies if this has been asked already: why can't the usage of at least some keywords as identifiers be allowed with the context of the usage being used to identify if a keyword or a variable is being referred to. For example, if = 3 # if is identifier if if = 3: # first if is keyword, second if is identifer A more complex usage may require some rules: a = not or and and ==> parse left to right to interpret as a = ( (not or) and (and) ). 'or' and the last 'and' are identifiers … [View More]

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Re: [Python-ideas] List Revolution
by Guido van Rossum Sept. 10, 2011

Sept. 10, 2011

On Sat, Sep 10, 2011 at 12:07 PM, Massimo Di Pierro <mdipierro(a)cs.depaul.edu> wrote: > Not to open a can of worms but why not use eval in this example? > It is faster. It is 5x more compact. It allows me to take advantage of the Python parser instead of reinventing the wheel. It is less error prone and easier to understand. It is a python keyword. It is unsafe (as the bug in your first version inadvertently illustrated :-). I don't actually quite follow what your example does (… [View More]

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Re: [Python-ideas] List Revolution
by Massimo Di Pierro Sept. 10, 2011

Sept. 10, 2011

On Sep 10, 2011, at 2:22 PM, Matt Billenstein wrote: > On Sat, Sep 10, 2011 at 02:14:13PM -0500, Massimo Di Pierro wrote: >> Not to open a can of worms but why not use eval in this example? >> It is faster. It is 5x more compact. It allows me to take advantage of the >> Python parser instead of reinventing the wheel. It is less error prone and >> easier to understand. It is a python keyword. > > I wouldn't worry too much about the implementation details of a … [View More]

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