On 20/04/2015 11:30, Steven D'Aprano wrote:
On Monday 20 April 2015 12:43, Rustom Mody wrote:
You've a 10-file python project in which you want to replace function 'f'
by function 'longname'
How easy is it?
About a thousand times easier than the corresponding situation:
You have ten PDF files in which you want to replace the word "f" with the
word "longname".
Why would the PDF example be particularly difficult? (I assume they can
simply be processed individually.)
Some tool would be used to edit the textual contents of the files, and,
in the absence of any more specific instructions (there being embedded
code examples for instance, or some literal uses of "f", or it's verse
that still needs to rhyme), then you just replace each whole-word "f"
with "longname".
(It might well be 1000 times harder if the PDFs contained full-featured
Postscript where all the "f"s are generated at runtime, or their glyphs
are formed with highly elaborate graphics.)
You have identified a weakness in the current Python ecosystem. Our
automated refactoring tools are currently quite weak and primitive.
I'm sure everyone is already aware of the difficulties with doing this
with Python code, but apart from comments and strings, there are
examples such as this:
if cond:
def f():
print ("This is F")
else:
f=3.142
x=f
In this last line, it's not possible to tell whether f refers to the
function, or the number. (I assume the requirement is to change calls to
f(), or any references to the name, to longname(), as well as the defs.)
Even harder is:
eval(s)
where the string s may also contain references to f.
There is also code that may be commented out temporarily that you want
to change, and other comments that you don't want to change. Etc.
With some languages the task is simpler, as what is or isn't a valid
reference to "f" can be determined by examining the source code.
(Although C gives Python a run for its money by being able to use its
macro system to make certain code impossible to analyse from the static
sources.)
--
Bartc
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