[Tutor] Lexer implementation

[Jason Doege]

Hi All,

 

Is there a classical way to implement a lexer in Python without using a
parser toolkit? Something like the lexer MJD illustrates in Higher Order
Perl, section 8.1.2. It's even better if it can act on a stream instead
of a string.

 

Best regards,

Jason Doege

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[Tutor] Dynamically changing a class

[Jason Doege]

Hi All,

I'd like to change the behavior of a class' member function dynamically
such that, once changed, all objects of the type would see the new
behavior.

For instance:

>>> class MyClass (object) :
  def mfunc(self, data):
print 'pre change behavior'

>>> aMyClassObj = MyClass()
>>> aMyClassObj.mfunc(data)
pre change behavior
>>> def MyClass.mfunc(self, data):  #this does not work :-(
  print 'post change behavior'

>>> aMyClassObj.mfunc(data)
post change behavior


Does anyone have any guidance on how to accomplish this? I'd also like
to be able to add and delete attributes, similarly.

Best regards,
Jason Doege
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Re: [Tutor] Dynamically changing a class

[Jason Doege]

Thanks for the good and useful information on this. Now for the why...

I am building an API and for various reasons I have chosen Python to
implement it. I'd like to separate the implementation from the interface
as, for instance, C++ does with separate .hpp and .cpp files. Apart from
defining a class with a bunch of empty methods and then redefining them,
I have not seen a good way to do this in Python. Can you recommend the
Pythonic way to do this?

Best regards,
Jason Doege
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