John Machin wrote:
On Apr 2, 2:10 am, John Posner <jjpos...@snet.net> wrote:
Dennis Lee Bieber presented a code snippet with two consecutive statements
that made me think, "I'd code this differently". So just for fun ... is
Dennis's original statement or my "_alt" statement more idiomatically
Pythonic? Are there even more Pythonic alternative codings?
mrkrs = [b for b in block
if b > 127
or b in [ "\r", "\n", "\t" ] ]
I'd worry about "correct" before "Pythonic" ... see my responses to
Dennis in the original thread.
mrkrs_alt1 = filter(lambda b: b > 127 or b in [ "\r", "\n", "\t" ],
block)
mrkrs_alt2 = filter(lambda b: b > 127 or b in list("\r\n\t"), block)
Comprehensions combine map and filter and somewhat, to some people,
replace both. Tastes vary.
If one has a filter function f already, filter(f,seq) may be faster than
(f(i) for i in seq). If one does not, (<expression involving i> for i
in seq) will probably be faster than filter(lambda i: <expression
imvolving i>, seq) as it avoids a function call, using inlined
expression code.
So either can be more Pythonic, depending on the context.
Try this on and see if it fits:
num_bin_chars = sum(b > "\x7f" or b < "\x20" and b not in "\r\n\t" for
b in block)
However, for just counting, this is even better -- and most Pythonic!
In fact, being able to count the number of True values in a stream of
True and False by summation is part of the justification of bool being a
subclass of int.
(Note: Dennis's statement converts a string into a list; mine does not.)
What is list("\r\n\t") doing, if it's not (needlessly) converting a
string into a list?
---
binary = (float(len(mrkrs)) / len(block)) > 0.30
binary_alt = 1.0 * len(mrkrs) / len(block) > 0.30
num_bin_chars > 0.30 * len(block)
(no mucking about with float() or 1.0, and it doesn't blow up on a
zero-length block)
Nice point!
Terry Jan Reedy
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