Syntax across languages

[Fredrik Lundh]

bearophileHUGS at lycos.com wrote:

> - Information about the current line and file as Ruby:
> __LINE__ __FILE__
> Instead of the python version:
> inspect.stack()[0][2] inspect.stack()[0][1]

(that's (mostly) CPython-dependent, and should be avoided)

> - ~== for approximate FP equality

str(a) == str(b)

> - comparison returns 4 values (i.e. inferior, equal, superior or not
> comparable), as in Pliant: "compare"

>>> cmp("a", "b")
-1
>>> cmp("a", "a")
0
>>> cmp("b", "a")
1
>>> cmp("ä", u"ä")
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
UnicodeDecodeError: 'ascii' codec can't decode byte /.../

sure looks like four possible outcomes.

> - identity function: "identity" as in Common Lisp (probably of little
> use in Python).

id(a)

> - Exception retrying: after catching an exception, tell the snippet to
> be re-run "retry" as in Ruby

>>> x = 0
>>> while 1:
...     try:
...         x += 1
...         if x <= 5:
...             raise ValueError
...     except ValueError:
...         print "retry"
...         continue
...     else:
...         break
...
retry
retry
retry
retry
retry
>>>

> - object cloning: obj.copy()  obj.deepcopy()

import copy

(cloning is usually a sign of a design problem in python.  if you think
you need it, you probably don't.  if you really think you need it, import
copy.)

> - recursive "flatten" as in Ruby (useful)

if you can define the semantics, it's a few lines of code.  if you're not
sure about the semantics, a built-in won't help you...

etc.

</F>