在Python中将字符串转换为整数表达式
假设我有这样一个字符串:在Python中将字符串转换为整数表达式,python,Python,假设我有这样一个字符串: "(((((908488990) - (255272197)) + ((-287634246) - (1144917742))) + (((1178779462) + (1410551276)) - ((-244815224) - (-722994984)))) + ((((-1134622847) - (-818189911)) + ((-479615696) + (-938948012))) + (((-1762293529) + (1281608170)) - (
"(((((908488990) - (255272197)) + ((-287634246) - (1144917742))) + (((1178779462) + (1410551276)) - ((-244815224) - (-722994984)))) + ((((-1134622847) - (-818189911)) + ((-479615696) + (-938948012))) + (((-1762293529) + (1281608170)) - ((1468184728) + (-895014314)))))"
在Python中,如何将其转换为如下表达式(不带引号):
(((((908488990) - (255272197)) + ((-287634246) - (1144917742))) + (((1178779462) + (1410551276)) - ((-244815224) - (-722994984)))) + ((((-1134622847) - (-818189911)) + ((-479615696) + (-938948012))) + (((-1762293529) + (1281608170)) - ((1468184728) + (-895014314)))))
这样我就可以得到这个表达式的结果:
-1457036634
使用
如果您想处理@hymms For Disco中提到的用户输入的字符串,那么使用eval可能是危险的 下面是一个关于如何处理此类字符串的示例,它有点长,部分可以放在子函数中,但它提供了正确的输出(加上括号检查):
希望它能对您有所帮助需要注意的是,您只能在可信/已知输入上使用
eval
,因为它可以执行危险代码。到目前为止,您做了什么?
eval("(((((908488990) - (255272197)) + ((-287634246) - (1144917742))) + (((1178779462) + (1410551276)) - ((-244815224) - (-722994984)))) + ((((-1134622847) - (-818189911)) + ((-479615696) + (-938948012))) + (((-1762293529) + (1281608170)) - ((1468184728) + (-895014314)))))")
test_string = r"(((((908488990) - (255272197)) + ((-287634246) - (1144917742))) + (((1178779462) + (1410551276)) - ((-244815224) - (-722994984)))) + ((((-1134622847) - (-818189911)) + ((-479615696) + (-938948012))) + (((-1762293529) + (1281608170)) - ((1468184728) + (-895014314)))))"
import operator
operators = {'+' : operator.add, '-' : operator.sub} # you can add other operators here like operator.multiply
def compute(string):
operator = None
value_left = None
it = iter(string)
while True:
try:
character = next(it)
except StopIteration:
break
if character ==' ': continue
if character == '(':
count = 1 #count open parenthesis
sub_string = ''
while True:
try:
character = next(it)
except StopIteration:
raise(EOFError("Not matching parenthesis"))
if character == '(':
count+=1
if character == ')':
if count == 1:
break
else:
sub_string+= character
count-=1
else:
sub_string+= character
if operator is None:
print('call compute with{}'.format(sub_string))
value_left = compute(sub_string)
continue
else:
return operator(value_left,compute(sub_string))
if character.isdigit():
temp_num = character
while character.isdigit() or character=='.':
try:
character = next(it)
except StopIteration:
break
temp_num+= character
if operator is None:
value_left = float(temp_num)
else:
return operator(value_left, float(temp_num))
if character in operators.keys():
operator = operators[character]
#test for unary '-' operator:
if character == '-' and value_left is None:
value_left = 0.0
return value_left
print(compute(test_string)) #returns -1457036634.0
test_string =r'(3+4'
print(compute(test_string)) # raises EOFError: Not matching parenthesis