如何在一些附加条件下将值插入python中的列表

Question

hi i have a list of tuples like this:

bigrams = [ ('wealth', 'gain'), ('gain', 'burnt'), ('burnt', 'will'), ('will', 'fire') ]

and i wish to append each individual tuple to a dictionary as the dictionarys key.

i want the format to look like this.

dict = {"wealth-gain": value, "gain-burnt": value ......} 

how would i create a loop that will go through each tuple in the bigrams list and append it to the dictionary?

Heres what i have

For word in bigrams:
    dict[(0+"-"+1) = dict

basicaly i want to take each tuple and add a "-" in between each word in the tuple then append that to a dictionary?

Any ideas how to do this?

Also if the bigram that is going to be appended to the dictionary matches a bigram that is already in the dictionary i would not like to add that bigram to the dictionary. Rather i would like to increment the value of the bigram already in the dictionary. Any ideas how to do that?

Thanks.

Answer 1

You can use the join method:

bigrams = [ ('wealth', 'gain'), ('gain', 'burnt'), ('burnt', 'will'), ('will', 'fire') ]
dict_ = {}
for tup in bigrams:
    k = '-'.join(tup)
    dict_[k] = data.setdefault(k,0) + 1

or express the initialization with a generator:

bigrams = [ ('wealth', 'gain'), ('gain', 'burnt'), ('burnt', 'will'), ('will', 'fire') ]
dict_ = dict(('-'.join(tup), 0) for tup in bigrams)

Answer 2

How about:

d = {}
val = 0
bigrams = [ ('wealth', 'gain'), ('gain', 'burnt'), ('burnt', 'will'), ('will', 'fire') ]
for word in bigrams:
    s = '-'.join(word)
    if s in d:
        d[s] += 1
    else:
        d[s] = val

Answer 3

You could use the tuples in the list directly as dictionary keys -- you do not need to join them to a single string. In Python 2.7, this gets particularly convenient in combination with collections.Counter :

from collections import Counter
bigrams = [('wealth', 'gain'), ('gain', 'burnt'),
           ('burnt', 'will'), ('will', 'fire')]
counts = Counter(bigrams)
print counts

prints

Counter({('gain', 'burnt'): 1, ('will', 'fire'): 1, ('wealth', 'gain'): 1, ('burnt', 'will'): 1})

Answer 4

You should make yourself familiar with list comprehension. That makes the transformation of the first list easier:

bigrams = [x+"-"+y for x,y in bigrams]

Now have a look at the setdefault method of dict and use it like this:

data = {} # dict is build in, so don't use it as variable name

for bigram in bigrams:
    data[bigram] = data.setdefault(bigram,0) + 1

If you want to have an even more compressed version, you might look at the itertools module.

Answer 5

try this:

bigrams = [ ('wealth', 'gain'), ('gain', 'burnt'), ('burnt', 'will'), ('will', 'fire') ]
bigram_dict = {}
for bigram in bigrams:
    key = '-'.join(bigram)
    if key in bigram_dict:
        bigram_dict[key] += 1
    else:
        bigram_dict[key] = 1

also, I feel obliged to point out that these are not bigrams in any way, shape or form. I'm not sure exactly what you mean to say, but they're certainly not bigrams!