On 2011/11/25 11:15 AM, lina wrote:
On Fri, Nov 25, 2011 at 5:05 PM, Christian Witts<cwi...@compuscan.co.za> wrote:
On 2011/11/25 10:41 AM, lina wrote:
pairs
{('66', '69'): 217, ('69', '66'): 75, ('64', '71'): 25}
such as here ('66', '69') and ('69', '66') is one key,
I wanna keep only one and add the value of those two keys, above is a
very simple example:
here is the (failed) code:
for k, v in pairs.items():
if str(k)[1]+str(k)[0] in pairs.keys():
print(pairs[str(k)[1]+str(k)[0]])
pairs[k]+=pairs[str(k)[1]+str(
k)[0]]
del pairs[str(k)[1]+str(k)[0]]
print(v,k)
Thanks for any advice,
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pairs.items() is fine if it's a small dictionary but for larger ones it's
going to slow things down as it generates the entire list of items before
you continue, rather use .iteritems() as it creates an iterator which only
yields one item at a time making it more efficient.
str(k)[1]+str(k)[0] is string concatenation so your first key tested is
'6669' and not ('66', '69') as you intended, you would have to create a new
tuple to get the key you wanted like `if (k[1], k[0]) in pairs.keys():`.
Also, your check to "in pairs.keys()" is wasteful as you generate a new list
of keys for every key and you will be better off using `in pairs:` directly
as it performs a dictionary lookup to test if the key exists.
With that in mind, this is how I would re-write that code segment. YMMV
for key in pairs.iterkeys():
# The [::-1] creates a reverse of the iterable so ('66', '69') will be
('69', '66')
$ python3 dehydron_data_stastic.py | sort -nr
Traceback (most recent call last):
File "dehydron_data_stastic.py", line 44, in<module>
for k in pairs.iterkeys():
AttributeError: 'dict' object has no attribute 'iterkeys'
if key[::-1] in pairs:
try:
# The first instance of the pair gets kept and the reversed gets
added
pairs[key] += pairs[key[::-1]]
del pairs[::-1]
except KeyError:
print "Key ('%s', '%s') already accumulated)" % key
Hope that helps.
--
Christian Witts
Python Developer
Ah, should have mentioned .iterkeys() / .itervalues() are in Python 2.x
and .keys() and .values() have been changed in Py3 to match .iter* from
Py2.x.
Just change that line to `for key in pairs.keys():` then.
--
Christian Witts
Python Developer
//
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