Matthias Gallé wrote:
Hi.
My problem is to replace all occurrences of a sublist with a new element.
Example:
Given ['a','c','a','c','c','g','a','c'] I want to replace all
occurrences of ['a','c'] by 6 (result [6,6,'c','g',6]).
For novelty value:
from itertools import izip
def replace2(data, pattern):
assert len(pattern) == 2
pattern = tuple(pattern)
icopy = iter(data)
icopy.next()
gen = izip(data, icopy)
while True:
item = gen.next()
if item == pattern:
yield '6'
gen.next()
else:
yield item[0]
# works if list ends with ['a', 'c']
data = ['g', 'a', 'c', 'a', 'c', 'a', 'a', 'a', 'g', 'a', 'c']
want = 'g66aaag6'
assert ''.join(replace2(data, ['a', 'c'])) == want
# otherwise you lose the last element of the tail
data = ['g', 'a', 'c', 'a', 'c', 'a', 'a', 'a', 'g', 'a', 'c', 'c', 'g']
want = 'g66aaag6cg'
get = 'g66aaag6c'
assert not ''.join(replace2(data, ['a', 'c'])) == want
assert ''.join(replace2(data, ['a', 'c'])) == get
# fix by adding the pattern to the end of the data as a sentinel
def replace2(data, pattern):
assert len(pattern) == 2
def _replace2(data, pattern):
pattern = tuple(pattern)
icopy = iter(data)
icopy.next()
gen = izip(data, icopy)
while True:
item = gen.next()
if item == pattern:
yield '6'
gen.next()
else:
yield item[0]
data = data + pattern
return list(_replace2(data, pattern))[:-1]
data = ['g', 'a', 'c', 'a', 'c', 'a', 'a', 'a', 'g', 'a', 'c']
want = 'g66aaag6'
assert ''.join(replace2(data, ['a', 'c'])) == want
data = ['g', 'a', 'c', 'a', 'c', 'a', 'a', 'a', 'g', 'a', 'c', 'c', 'g']
want = 'g66aaag6cg'
assert ''.join(replace2(data, ['a', 'c'])) == want
print 'done'
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