python 用不同的值替换多次出现的字符串

Question

i am writing a script in python that replaces all the occurrences of an math functions such as log with there answers but soon after i came into this problem i am unable replace multiple occurrences of a function with its answer

    text = "69+log(2)+log(3)-log(57)/420"
    log_list = []
    log_answer = []
    z = ""
    c = 0
    hit_l = False
    for r in text:
        if hit_l:
            c += 1
            if c >= 4 and r != ")":
                z += r
            elif r == ")":
                hit_l = False
        if r == "l":
            hit_l = True
        log_list.append(z)

    if z != '':
        logs = log_list[-1]
        logs = re.sub("og\\(", ";", logs)
        log_list = logs.split(";")
        for ans in log_list:
            log_answer.append(math.log(int(ans)))
    for a in log_answer:
        text = re.sub(f"log\\({a}\\)", str(a), text)

i want to replace log(10) and log(2) with 1 and 0.301 respectively i tried using re.sub but it is not working i am not able to replace the respective functions with there answers any help will be appreciated thank you

Answer 1

As long as your string contains no spaces and there are + signs between different logarithmic functions, eval could be a way to do it.

>>> a = 'log(10)+log(2)'
>>> b = a.split('+')
>>> b
['log(10)', 'log(2)']

>>> from math import log10 as log
>>> [eval(i) for i in b]
[1.0, 0.3010299956639812]

EDIT: You could repeatedly use str.replace method to replace all mathematical operators (if there are more than one) with whitespaces and eventually use str.split like:

>>> text.replace('+', ' ').replace('-', ' ').replace('*', ' ').replace('/', ' ').split()
['69', 'log(2)', 'log(3)', 'log(57)', '420']

Answer 2

Here is my take on this using eval along with re.sub with a callback function:

x = "log(10)+log(2)"
output = re.sub(r'log\((\d+(?:\.\d+)?)\)', lambda x: str(eval('math.log(' + x.group(1) + ', 10)')), x)
print(output)  # 1.0+0.301029995664