How to print floating point in scientific format?

[sdhyok]

As you recommend, I won't modify the default behavior of python.
But, still I need a better treatment of python on arrays.

Daehyok Shin

Alex Martelli <aleax at aleax.it> wrote in message news:<aL9Za.34994$an6.1223329 at news1.tin.it>...
> sdhyok wrote:
> 
> > I want to change the DEFAULT behavior of python
> > to print out all floating points in scientific format?
> > For instance,
> > 
> >>x=0.01
> >>print x
> > 1.000000E-2 #Like print "%E"%x
> > 
> > How can I do it?
> 
> You need to download Python's sources, modify them, and build a modified
> Python interpreter and libraries that impose the behavior you want rather
> than what the normal Python interpreter and libraries do.
> 
> Specifically, look at function format_float, line 233 of file
> Objects/floatobject.c in the current 2.3 maintenance branch for example.
> Currently it formats the float with "%.*g" [variable precision passed
> in as an argument to format_float]; if you want to use a different C level
> format string, that string is the one you need to change.
> 
> Of course, that's likely to break some of the tests in Python's unit-tests
> suite, so you'll probably want to modify those, too.  And then, you get to
> maintain your "slightly divergent" Python yourself forevermore.  I do not
> think there is much likelihood that a patch in this regard would be
> accepted in the Python core, even if you made it flexible enough to keep
> the current behavior by default and change it only upon specific request
> (e.g., use a variable string for the format, and let the Python coder
> modify the letter in it, only, keeping "%.*g" as the default but letting
> the 'g' be changed) -- such "big global" settings, which would let one
> idiosyncratic library module modify Python behavior enough to break other
> innocent modules, are looked at with disfavour, for reasons that should
> be obvious (each and every such 'big global' _damages_ Python's suitability
> for writing very large, multi-authors applications -- that suitability is
> currently very high, and _extremely_ convincing arguments would need to
> be brought to bear in order to convince Guido to deliberately lower it).
> 
> 
> Alex