Using python for _large_ projects like IDE

[Sridhar R]

Hi,

I am a little experienced python programmer (2 months).  I am somewhat
experienced in C/C++.  I am planning (now in design stage) to write an
IDE in python.  The IDE will not be a simple one.  I had an idea of
writing the IDE in C/C++, as it is a big project, bcoz of the
following

1. if python is used, then the memory required for running the IDE
will be high.
2. if pure python is used, the IDE will be slower.

I'm not sure whether they are true.

Then I thought of using python for 90% of the code and using C for
other performance critical part.  But the problem is in identifying
the performance critical code.  People suggest to start with pure
python and then _recode_ the performance critical code after profiling
the original code.  But I fear whether there will be a conflit in say
data structures.  Not yet expert in extending/embedding python.
Are there any ways to forsee the performance critical parts?

Also, any suggestions on reducing memory usage of big applications
written in python?