为列表中的每个字符串分配一个数字。 Python 3.6

Question

I am trying to to write a code that takes input, splits it into a list, and then assigns a number to each string in the list.

For example: If my input was "hello hello goodbye hello" Then it would output "1121".

This is the code I have written so far:

sentence = input("What is your sentence? ").lower()
list_s = str.split(sentence)
for i in range(len(list_s)):

Answer 1

Use a dictionary containing the strings as keys and the number as value:

inp = 'hello hello world hello'
d = {}
idx = 1
for word in inp.lower().split():
    # If the word is in the dictionary print the corresponding number
    if word in d:
        print(d[word], end='')
    # Otherwise print the next number and add the number to the dictionary
    else:
        print(idx, end='')
        d[word] = idx
        idx += 1

I proposed the dictionary because the in operation is very fast and one needs to store 2 things: The string and the value. Making the dictionary a very suitable data structure for that problem.

If you like it shorter you could use a list comprehension (using the len(d)+1 "trick" from trincots answer):

inp = 'hello hello world hello'
d = {}
result = [d.setdefault(word, len(d)+1) for word in inp.lower().split()]

Where result would be a list containing [1, 1, 2, 1] which you could print using:

print(''.join(map(str, result)))

Or (thanks Stefan Pochmann for the hint):

print(*result, sep="")

Answer 2

As MSeifert, I would suggest a dictionary. You can produce the assigned number from the size of the dictionary at the moment a new word is added. The final result can be produced as a list with list comprehension:

list_s = str.split("hello hello goodbye hello")
d = {} # a dictionary, which will store for each word a number
for word in list_s:
    if not word in d: # first time we see this word?
        d[word] = len(d)+1 # assign to this word a unique number
result = [d[word] for word in list_s] # translate each word to its unique number
print (result) # [1, 1, 2, 1]

Answer 3

You can use a set :

def get_numbers(s):
   s = s.split()
   new_s = [a for i, a in enumerate(s) if a not in s[:i]]
   return [new_s.index(i)+1 for i in s]

l = ["hello hello goodbye hello", "hello goodbye hello hello"]
final_l = list(map(get_numbers, l))

Output:

[[1, 1, 2, 1], [1, 2, 1, 1]]