将字母列表转换为数字列表

Question

I need to turn a list of numbers into a list of letters.

More specifically, I need to read PZ and turn it into PZx , such that the first distinct letter appearing in PZ assumes in PZx the number 1 , the second distinct letter assumes the number 2 , the third distinct letter assumes the number 3 , and the fourth distinct letter assumed the number 4 . Example:

PZ = ['R','O','B','O','R','R','B','G','O','G','B','G']

PZx = [1,2,3,2,1,1,3,4,2,4,3,4]

I need to write a function that turns any given PZ into PZx according to this rule.

Answer 1

You could use a dictionary and setdefault , from the documentation:

If key is in the dictionary, return its value. If not, insert key with a value of default and return default. default defaults to None.

Code:

PZ = ['R','O','B','O','R','R','B','G','O','G','B','G']
uniques = {}
PZx = [uniques.setdefault(l, len(uniques) + 1) for l in PZ]
print(PZx)

Output

[1, 2, 3, 2, 1, 1, 3, 4, 2, 4, 3, 4]

Answer 2

I think you can use list index and have a simple loop like this

occured = []
for item in PZ:
    if item not in occured:
        occured.append(item)
    PZx.append(occured.index(item) + 1)

Answer 3

In [1]: PZ = ['R','O','B','O','R','R','B','G','O','G','B','G']

In [2]: d = {}

In [3]: PZx = []

In [4]: n = 1
In [5]: for x in PZ:
...:     if x not in d:
...:         d[x] = n
...:         n += 1
...:     PZx += [d[x]]
...:

In [6]: PZx
Out[6]: [1, 2, 3, 2, 1, 1, 3, 4, 2, 4, 3, 4]

Answer 4

This could be done easily with a dictionary. Try something like this.

PZ = ['R','O','B','O','R','R','B','G','O','G','B','G']
PZx = []
dict = {}
count = 1

for letter in PZ:
    if letter not in dict.keys():
        dict[letter] = count
        PZx.append(dict[letter])
        count+=1
    else:
        PZx.append(dict[letter])

now PZx should equal [1,2,3,2,1,1,3,4,2,4,3,4]

Answer 5

Another way to do it by using pandas and list comprehension:

import pandas as pd

PZ = ['R', 'O', 'B', 'O', 'R', 'R', 'B', 'G', 'O', 'G', 'B', 'G']
PZ_unique = pd.unique(PZ).tolist()  # ['R', 'O', 'B', 'G']
PZx = [PZ_unique.index(pz) + 1 for pz in PZ]  # [1, 2, 3, 2, 1, 1, 3, 4, 2, 4, 3, 4]