当项目包含方括号时，将大字符串转换为浮点数列表

Question

I have a variable r that contains a string, however I need it to be a list of floats. This has been covered multiple times in this forum, however I can't seem to find one that matches this case:

>>> print r
[0.06481481481481466, 0.06481481481481466, 0.06481481481481466, 0.0754716981132074, 0.07619047619047604, 0.07619047619047604, 0.07692307692307698, 0.07766990291262142, 0.07766990291262142, 0.07843137254901968, 0.07920792079207928, 0.07920792079207928, 0.08000000000000007, 0.08000000000000007]
>>> type(r)
<type 'str'>

When I try to split it...

    >>> r.split(',')
['[0.06481481481481466', ' 0.06481481481481466', ' 0.06481481481481466', ' 0.0754716981132074', ' 0.07619047619047604', ' 0.07619047619047604', ' 0.07692307692307698', ' 0.07766990291262142', ' 0.07766990291262142', ' 0.07843137254901968', ' 0.07920792079207928', ' 0.07920792079207928', ' 0.08000000000000007', ' 0.08000000000000007]']

Now the first and last item in r contain a '[' and ']' respectively. So obviously, in order to convert this into a float, I need to remove these.

This is what I have gotten up to, but it doesn't seem to work...

def stringlist_to_floatlist(e):
    split = e.split(',')
    l = len(split)
    for i in split:
        for br in ["[","]"]:
            if br in i:
                try:
                    i = float(i.replace(br,""))
                except TypeError:
                    continue
            else:
                try:
                    i = float(i)
                except TypeError:
                    continue
    return i 


>>> stringlist_to_floatlist(r)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "<stdin>", line 6, in stringlist_to_floatlist
TypeError: argument of type 'float' is not iterable

Answer 1

>>> ast.literal_eval('[0.06481481481481466, 0.06481481481481466, 0.06481481481481466, 0.0754716981132074, 0.07619047619047604, 0.07619047619047604, 0.07692307692307698, 0.07766990291262142, 0.07766990291262142, 0.07843137254901968, 0.07920792079207928, 0.07920792079207928, 0.08000000000000007, 0.08000000000000007]')
[0.06481481481481466, 0.06481481481481466, 0.06481481481481466, 0.0754716981132074, 0.07619047619047604, 0.07619047619047604, 0.07692307692307698, 0.07766990291262142, 0.07766990291262142, 0.07843137254901968, 0.07920792079207928, 0.07920792079207928, 0.08000000000000007, 0.08000000000000007]
>>> ast.literal_eval('[0.06481481481481466, 0.06481481481481466, 0.06481481481481466, 0.0754716981132074, 0.07619047619047604, 0.07619047619047604, 0.07692307692307698, 0.07766990291262142, 0.07766990291262142, 0.07843137254901968, 0.07920792079207928, 0.07920792079207928, 0.08000000000000007, 0.08000000000000007]')[0]
0.06481481481481466

Answer 2

The other answers here work well, but since it seems you're getting this string from an outside source, it's likely that you're parsing json formatted strings. Python has a built-in json parser, so you can just do:

>>> import json
>>> r = """[0.06481481481481466, 0.06481481481481466, 0.06481481481481466, 0.0754716981132074, 0.07619047619047604, 0.07619047619047604, 0.07692307692307698, 0.07766990291262142, 0.07766990291262142, 0.07843137254901968, 0.07920792079207928, 0.07920792079207928, 0.08000000000000007, 0.08000000000000007]"""
>>> json.loads(r)
[0.06481481481481466, 0.06481481481481466, 0.06481481481481466, 0.0754716981132074, 0.07619047619047604, 0.07619047619047604, 0.07692307692307698, 0.07766990291262142, 0.07766990291262142, 0.07843137254901968, 0.07920792079207928, 0.07920792079207928, 0.08000000000000007, 0.08000000000000007]
>>> type(json.loads(r))
list

Answer 3

Although python has specific tools for parsing json and other formats, if you have a string that is generally bracketed by some characters at the beginning and end that you want to get rid of, you can specify those characters with the strip string builtin:

>>> s = '[4.4,3.2,1.1]'
>>> s.strip('[]')
'4.4,3.2,1.1'
>>> s = '[I am not: a ; valid .,:{json string]'
>>> s.strip('[]')
'I am not: a ; valid .,:{json string'