如何将字符串列表转换为整数列表

Question

In the below part of code v is a list of characters.

import collections
import csv
import sys


with open("prom output.csv","r") as f:
    cr = csv.reader(f,delimiter=",")
    d=collections.defaultdict(lambda : list())
    header=next(cr)    

    for r in cr:
        d[r[0]].append(r[1])   


with open("sorted output.csv","w") as f:
    cr = csv.writer(f,sys.stdout, lineterminator='\n')
    od = collections.OrderedDict(sorted(d.items()))

    for k,v in od.items():  
        cr.writerow(v)  

My output looks like

I want to map all the characters of my input into an integer, so that instead of a table with characters i get a table with numbers. I tried to use the built in function ord() but it doesnt work, since it only accepts single characters as input and not lists. Can you help?

Answer 1

If you have a list of letters that you want converting into numbers try:

>>> [ord(l) for l in letters]
[97, 98, 99, 100, 101, 102, 103]

or

>>> list(map(ord, letters))
[97, 98, 99, 100, 101, 102, 103]

Or if you're dealing with capitalized column headings and want the corresponding index

>>> letters = ['A', 'B', 'C', 'D', 'E']
>>> [ord(l.lower()) -96 for l in letters]
[1, 2, 3, 4, 5]

Answer 2

You can use map() to apply an operation to each item in a list:

a = ['a', 'b', 'c']
b = map(lambda c: ord(c), a)

print b
>>> [97, 98, 99]