我试图制作一个不使用eval()的计算器，并将整个方程作为字符串.此外，我不能使用任何库、模块等.我已经设法制作了一些东西，但我不知道如何先做乘法和除法，然后再做其余的.
4 + 4 * 4 = 20
4 + 4 * 4 + 4 = 4
编辑:所以我找到了问题所在，但它仍然不能正常工作.问题是代码甚至没有到达找到"*"的部分.我会用箭在它够不着的地方做标记.
以下是代码，请提前感谢:
print("Calculator")
# All the numbers
def numbers(num):
return(
num == "0"
or num == "1"
or num == "2"
or num == "3"
or num == "4"
or num == "5"
or num == "6"
or num == "7"
or num == "8"
or num == "9"
)
# All the operators
def operator(oprt):
return(
oprt == "+"
or oprt == "-"
or oprt == "*"
or oprt == "/"
)
# Removes all the spaces
def remove_spaces(string):
string = string.replace(" ", "")
return string
# Does the math between two numbers
def operation(string, num1, num2):
if string == "+":
return num1 + num2
if string == "-":
return num1 - num2
if string == "*":
return num1 * num2
if string == "/":
return num1 / num2
# Tests how long the number is
def test_number(numstr):
n = 0
num = ""
try:
while numbers(numstr[n]):
num += numstr[n]
n += 1
except:
pass
return(int(num), n)
# Solves the equation
def eval_equation(eq):
negative = False
# Removes the spaces
eq = remove_spaces(eq)
while True:
try:
# Checks if the first number is negative
if eq[0] == "-":
negative = True
eq = eq[1:]
# Solves the multiplication first
i = 0
eqTemp = ""
if "*" in eq:
try:
while i < len(eq):
if eq[i] == "+" or eq[i] == "-" or eq[i] == "/":
eqTemp = eqTemp + eq[:i + 1]
print(f"eqTemp = {eqTemp}")
eq = eq[i + 1:]
print(f"eq = {eq}")
elif eq[i] == "*": # <-------this is the problem----
break
print(f"eqTemp = {eqTemp}")
print(f"eq = {eq}")
i += 1
except:
i = 0
# Checks the lenght of the number
number1 = test_number(eq)[0]
# Returns the "-" in the negative number
if negative == True:
number1 = -number1
negative = False
# Removes the first number from the string to continue with the next
endNumber1 = test_number(eq)[1]
eq = eq[endNumber1:]
# Checks for any more numbers
if eq == "":
return number1
# This is the operator sign
op = eq[0]
eq = eq[1:]
# Repeats the same process with the other number
number2 = test_number(eq)[0]
endNumber2 = test_number(eq)[1]
result = operation(op, number1, number2)
# Takes the result and passes it as to the first number along with the rest of the equation
number1 = result
eq = str(number1) + eq[endNumber2:]
eq = eqTemp + eq
except Exception as error:
print(error)
break
return number1
# Main function
if __name__ == "__main__":
while True:
equation = input(": ")
print(eval_equation(equation))