Re: searching for strings (in a tuple) in a string
Simon Forman wrote: ... I usually use this with assert statements when I need to check a sequence. Rather than: for something in something_else: assert expression I say assert False not in (expression for something in something_else) This way the whole assert statement will be removed if you use the '-O' switch to the python interpreter. (It just occurred to me that that's just an assumption on my part. I don't know for sure that the interpreter isn't smart enough to remove the first form as well. I should check that. ;P ) FWIW I did just check that and it seems valid, the second form gets optimized away. File delme.py: import dis N = (True, True, False) def a(): for n in N: assert n def b(): assert False not in (n for n in N) dis.dis(a) print '===' dis.dis(b) Results of running it without '-O': $ python delme.py 8 0 SETUP_LOOP 28 (to 31) 3 LOAD_GLOBAL 0 (N) 6 GET_ITER 7 FOR_ITER20 (to 30) 10 STORE_FAST 0 (n) 9 13 LOAD_FAST0 (n) 16 JUMP_IF_TRUE 7 (to 26) 19 POP_TOP 20 LOAD_GLOBAL 2 (AssertionError) 23 RAISE_VARARGS1 26 POP_TOP 27 JUMP_ABSOLUTE7 30 POP_BLOCK 31 LOAD_CONST 0 (None) 34 RETURN_VALUE === 13 0 LOAD_GLOBAL 0 (False) 3 LOAD_CONST 1 (code object generator expression at 0xb7d89ca0, file delme.py, line 13) 6 MAKE_FUNCTION0 9 LOAD_GLOBAL 1 (N) 12 GET_ITER 13 CALL_FUNCTION1 16 COMPARE_OP 7 (not in) 19 JUMP_IF_TRUE 7 (to 29) 22 POP_TOP 23 LOAD_GLOBAL 2 (AssertionError) 26 RAISE_VARARGS1 29 POP_TOP 30 LOAD_CONST 0 (None) 33 RETURN_VALUE Results of running it with '-O': $ python -O delme.py 8 0 SETUP_LOOP 14 (to 17) 3 LOAD_GLOBAL 0 (N) 6 GET_ITER 7 FOR_ITER 6 (to 16) 10 STORE_FAST 0 (n) 9 13 JUMP_ABSOLUTE7 16 POP_BLOCK 17 LOAD_CONST 0 (None) 20 RETURN_VALUE === 13 0 LOAD_CONST 0 (None) 3 RETURN_VALUE -- http://mail.python.org/mailman/listinfo/python-list
Re: searching for strings (in a tuple) in a string
On Thu, 06 Jul 2006 04:45:35 -0700, manstey wrote:
Hi,
I often use:
a='yy'
tup=('x','yy','asd')
if a in tup:
...
but I can't find an equivalent code for:
a='xfsdfyysd asd x'
tup=('x','yy','asd')
if tup in a:
...
Of course you can't. Strings don't contain tuples, since they are utterly
different kinds of objects.
I can only do:
if 'x' in a or 'yy' in a or 'asd' in a:
...
but then I can't make the if clause dependent on changing value of tup.
Sure you can.
a = 'xfsdfyysd asd x'
tup = ('x','yy','asd')
for item in tup:
if item not in a:
print Item missing
break
else:
print All items found.
It's a little verbose, but you can stick it into a function definition and
use it as a one-liner.
Or, use a list comprehension:
a = 'xfsdfyysd asd x'
tup = ('x','yy','asd')
if [item for item in tup if item in a]:
print Some items found.
else:
print No items found.
Or, you can use filter:
a = 'xfsdfyysd asd x'
tup = ('x','yy','asd')
if filter(lambda item, a=a: item in a, tup):
print Some items found.
else:
print No items found.
However, keep in mind that in has a subtly different effect in strings
and tuples.
x in (x, y) is true, but x in (xy, yy) is not, as you would
expect. However, the situation for strings isn't quite the same:
x in x y is true, but so is x in xx yy.
One way around that is to convert your string a into a list:
a = 'xfsdfyysd asd x'
a = a.split() # split on any whitespace
and now your tests will behave as you expected.
--
Steven.
--
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Re: searching for strings (in a tuple) in a string
You can get the matching elements with a list comprehension with
something like
py a='xfsdfyysd asd x'
py tup=('x','yy','asd')
py [x for x in tup if x in a.split()]
['x', 'asd']
Hope this helps
manstey wrote:
Hi,
I often use:
a='yy'
tup=('x','yy','asd')
if a in tup:
...
but I can't find an equivalent code for:
a='xfsdfyysd asd x'
tup=('x','yy','asd')
if tup in a:
...
I can only do:
if 'x' in a or 'yy' in a or 'asd' in a:
...
but then I can't make the if clause dependent on changing value of tup.
Is there a way around this?
--
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Re: searching for strings (in a tuple) in a string
manstey [EMAIL PROTECTED] wrote:
but I can't find an equivalent code for:
a='xfsdfyysd asd x'
tup=('x','yy','asd')
if tup in a:
...
I can only do:
if 'x' in a or 'yy' in a or 'asd' in a:
...
but then I can't make the if clause dependent on changing value of tup.
Is there a way around this?
is the def statement broken in your Python version ?
def findany(text, words):
for w in words:
if w in text:
return True
return False
if findany(a, tup):
...
/F
--
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Re: searching for strings (in a tuple) in a string
I know I can do it this way. I wanted to know if there was another way.
Fredrik Lundh wrote:
manstey [EMAIL PROTECTED] wrote:
but I can't find an equivalent code for:
a='xfsdfyysd asd x'
tup=('x','yy','asd')
if tup in a:
...
I can only do:
if 'x' in a or 'yy' in a or 'asd' in a:
...
but then I can't make the if clause dependent on changing value of tup.
Is there a way around this?
is the def statement broken in your Python version ?
def findany(text, words):
for w in words:
if w in text:
return True
return False
if findany(a, tup):
...
/F
--
http://mail.python.org/mailman/listinfo/python-list
Re: searching for strings (in a tuple) in a string
manstey [EMAIL PROTECTED] wrote: I know I can do it this way. I wanted to know if there was another way. if you don't want to write Python programs, why are you using Python ? /F -- http://mail.python.org/mailman/listinfo/python-list
Re: searching for strings (in a tuple) in a string
manstey wrote:
Hi,
I often use:
a='yy'
tup=('x','yy','asd')
if a in tup:
...
but I can't find an equivalent code for:
a='xfsdfyysd asd x'
tup=('x','yy','asd')
if tup in a:
...
I can only do:
if 'x' in a or 'yy' in a or 'asd' in a:
...
but then I can't make the if clause dependent on changing value of tup.
Is there a way around this?
One thing I do sometimes is to check for True in a generator
comprehension
if True in (t in a for t in tup):
# do whatever here
Because you're using a generator you get the same short-circut
behavior that you would with a series of 'or's, the if statement won't
bother checking the rest of the terms in tup after the first True
value.
def f(n, m):
print n
return n m
m = 2
if True in (f(n, m) for n in range(5)):
print 'done'
0
1
2
3
done
# See? No 4! :-)
I usually use this with assert statements when I need to check a
sequence. Rather than:
for something in something_else: assert expression
I say
assert False not in (expression for something in something_else)
This way the whole assert statement will be removed if you use the '-O'
switch to the python interpreter. (It just occurred to me that that's
just an assumption on my part. I don't know for sure that the
interpreter isn't smart enough to remove the first form as well. I
should check that. ;P )
Note, in python 2.5 you could just say
if any(t in a for t in tup):
# do whatever here
In your case though, if I were doing this kind of thing a lot, I would
use a little helper function like the findany() function Fredrik Lundh
posted.
IMHO
if findany(a, tup):
...
is much clearer and readily understandable than mucking about with
generator comprehensions...
Peace,
~Simon
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