[Python-ideas] List Revolution

[Massimo Di Pierro]

Of course. It was a proof of concept. Here is with an inline parser:

class List(list):
    """                                                                                                                                                                                  
    >>> a=List()                                                                                                                                                                         
    >>> 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.onethousandfivehundredthirtyeighth                                                                                                                                       
    1537                                                                                                                                                                                 
    """
    def __getattr__(self,name):
        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 = [
            ("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"),
            ("fifty","+50"),
            ("sixty","+60"),
            ("seventy","+70"),
            ("eighty","+80"),
            ("ninety","+90"),
            ("one","+1"),
            ("two","+2"),
            ("three","+3"),
            ("four","+4"),
            ("five","+5"),
            ("six","+6"),
            ("seven","+7"),
            ("eigth","+8"),
            ("nine","+9"),
            ("ten","+10"),
            ("hundred",")*100+("),
            ("thousand",")*1000+("),
            ("million",")*1000000+("),
            ("billion",")*1000000000+("),
            ("trillion",")*100000000000+("),
            ("and","")]
        for key,value in subs: name = name.replace(key,value)
        if '(' in name: name='('+name+')'
        name.replace('()','1')
        ## parser                                                                                                                                                                        
        import re
        tokenizer = re.compile('\+|\(\+|\(|\)|\*|[\d]+')
        stack = [0]
        while name:
            token = tokenizer.match(name)
            if not token: raise AttributeError
            if token.group() in ('(','(+'): stack.append(0)
            if token.group().isdigit(): stack.append(int(token.group()))
            if token.group() in ')+' and len(stack)>1: stack[-2:]=[stack[-1]+stack[-2]]
            if token.group()=='*':
                name = name[1:]
                token = tokenizer.match(name)
                if not token or not token.group().isdigit(): raise AttrbuteError
                stack[-1:]=[stack[-1]*int(token.group())]
            name = name[token.end():]
        number = sum(stack)
        ## end parser                                                                                                                                                                    
        try: return self[number-1]
        except: raise IndexError




On Sep 10, 2011, at 1:00 PM, Guido van Rossum wrote:

> I thought we were all just having a little bit of fun with what's
> obviously the least-likely-to-be-accepted proposal to have hit
> python-ideas in a long time; and now I see serious questions about it
> on Twitter and Quora... Time to start adding smileys to all posts! :-)
> 
> (Though seriously, Massimo, you should be able to implement the same
> idea without using eval() at all.)
> 
> --Guido
> 
> On Sat, Sep 10, 2011 at 10:50 AM, Massimo Di Pierro
> <massimo.dipierro at gmail.com> wrote:
>> Anyway ... mine was not a serious proposal. I like python lists as they are.
>> 
>> On Sep 10, 2011, at 12:43 PM, Devin Jeanpierre wrote:
>> 
>>>> Damn dollar signs.
>>>> if not re.compile('^[\d\+\*\(\)]+$').match(name): return AttributeError
>>> 
>>> '(2**1024)**(2**1024)' etc.
>>> 
>>> Devin
>>> 
>>> On Sat, Sep 10, 2011 at 1:05 PM, Massimo Di Pierro
>>> <massimo.dipierro at gmail.com> wrote:
>>>> LOL.
>>>> 
>>>> Damn dollar signs.
>>>> if not re.compile('^[\d\+\*\(\)]+$').match(name): return AttributeError
>>>> 
>>>> On Sep 10, 2011, at 11:45 AM, Stefan Behnel wrote:
>>>> 
>>>>> Massimo Di Pierro, 10.09.2011 18:35:
>>>>>> [...]
>>>>>>         if not re.compile('[\d\+\*\(\)]+').match(name): return 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.
>>>>> 
>>>>> Nice try. And it would even be ok if you had assured that the *entire* expression was validated against the regex.
>>>>> 
>>>>> Stefan
>>>>> 
>>>>> _______________________________________________
>>>>> Python-ideas mailing list
>>>>> Python-ideas at python.org
>>>>> http://mail.python.org/mailman/listinfo/python-ideas
>>>> 
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>>>> 
>> 
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> 
> 
> 
> -- 
> --Guido van Rossum (python.org/~guido)