Python: replace list items and produce all possible permutations - python-3.x

Question

I am trying to implement morse decode for partial morse code.Say for example the representation of word TEST in morse code is ['-','.','...','-'] however if the first character of every morse code string is missing and represented by x then partial morse code for TEST will become ['x','x','x..','x'].Thus in order to decode this partial message, we will have to replace x with either. or - for every occurrence of x in above partial morse code.With 'x' unknown the permutations of TEST word on decoding would be ETST,EEDT,ETSE etc.I have implemented the morse partial decode function as below:
def morsePartialDecode(inputStringList):
with open('words.txt','a') as wordfile:
dictionaryFileLoc = './dictionary.txt'
message_received = inputStringList
message_received = ' '.join(inputStringList)
for i in range(len(message_received)):
x = 'x'
y = '.'
message = message_received.replace(x, y)
message1 = message.split(",")
message_converted = morseDecode(message1)
print message_converted
print >> wordfile, (message_converted)
for i in range(len(message_received)):
x = 'x'
y = '-'
message = message_received.replace(x, y)
message2 = message.split(",")
message_converted = morseDecode(message2)
print >> wordfile, (message_converted)
elements = []
wordfile.closed
return message_converted
def partialMorseCodeTest():
test = ['x', 'x', 'x..', 'x']
print morsePartialDecode(test)
partialMorseCodeTest()
Output:
EESE
TTDT
I need all the combinations of ['x','x','x..','x'] with x replaced by . or -.And my morseDecode() will convert each combination to respective words like EESE, TTDT etcmorsedecode)What to do.Thanks in advance!

Answer 1

Great case for itertools
Example using itertools.product:
from itertools import product
def replace_x_with_all_combinations(morse):
# only works with 1 and 1 only 'x' in each element
all_perm = list()
for v in morse:
if 'x' in v:
# create a list of permutations per element of the morse list
# and append them to the all_perm list
all_perm.append([v.replace('x','.'), v.replace('x','-')])
else:
# if no x found, then append the original element
all_perm.append([v])
# all_perm = [['.', '-'], ['.', '-'], ['...', '-..'], ['.', '-']]
# the list all_perm needs to be unpacked before passing
# to the product() generator, hence the *
return list(product(*all_perm))
partial = ['x','x','x..','x']
result = replace_x_with_all_combinations(partial)
for e in result:
print(e)
Output:
('.', '.', '...', '.')
('.', '.', '...', '-')
('.', '.', '-..', '.')
('.', '.', '-..', '-')
('.', '-', '...', '.')
('.', '-', '...', '-')
('.', '-', '-..', '.')
('.', '-', '-..', '-')
('-', '.', '...', '.')
('-', '.', '...', '-')
('-', '.', '-..', '.')
('-', '.', '-..', '-')
('-', '-', '...', '.')
('-', '-', '...', '-')
('-', '-', '-..', '.')
('-', '-', '-..', '-')
[EDIT]
Although I put the restriction in the above code myself, the "works only for 1 x in the morse character" bugged me, so the following example will take more than one digit missing from a morse character, more than one 'x'
from itertools import product
def replace_x_in_morse_charcter(morse_character):
all_perm = [['.','-'] if c == 'x' else [c] for c in morse_character]
p = list(product(*all_perm))
return [''.join([v for v in e]) for e in p]
def replace_x_in_morse_word(morse):
all_perm = [replace_x_in_morse_charcter(c) for c in morse]
return list(product(*all_perm))
partial = ['x','x','x..','xx']
result = replace_x_in_morse_word(partial)
for e in result:
print(e)
[EDIT] for fun a one liner:
morse_word = ['x','x','x..','xx']
result = list(product(*[[''.join([v for v in e]) for e in list(product(*[['.','-'] if c == 'x' else [c] for c in cm]))] for cm in morse_word]))