Question

我在python上相当新，所以我对它不太了解。我做了一个计算器，我希望它接受一个：

ans()

输入。目前，如果存在[0-9 * / - +]以外的某些内容，则有一个部分阻止程序执行输入，因此它不会崩溃。我怎么做

ans()

表示最后输入的等式的输出，因此我可以输入如下内容：

>> 8*8 #last input
64 #last output
>> ans()*2 #current input
128 # current output

希望我正确地解释了一切，这是我的代码：

valid_chars = "0123456789-+/* \n";
    while True:
    x = "x="
    y = input(" >> ")
    x += y
    if any(c not in valid_chars for c in y):
        print("WARNING: Invalid Equation")
        continue
    try:
        exec(x)
    except (SyntaxError, ZeroDivisionError):
        print ("WARNING: Invalid Equation")
    else:
        print(x)

更新：我添加了几行，但它不会运行：

valid_chars = "0123456789-+/* \n";
while True:
    x = "x="
    y = input(" >> ")
    x += y
    def ans():
        return _
    def ans():
        try:
            return _
    except NameError:
        return 0 # appropriate value
    if any(c not in valid_chars for c in y):
        print("WARNING: Invalid Equation")
        continue
    try:
        exec(x)
    except (SyntaxError, ZeroDivisionError):
        print ("WARNING: Invalid Equation")
    else:
        print(x)

错误：NameError

以外的“意外缩进”

我做错了什么，如何解决这个问题？感谢

更新

好吧，我修好了：

valid_chars = "0123456789-+/*ans() \n"
while True:
    x = "x="
    y = input(" >> ")
    x += y
    def ans():
        return z
    def ans():
        try:
            return z
    except NameError:
        return 0 # appropriate value
    if any(c not in valid_chars for c in y):
        print("WARNING: Invalid Equation")
        continue
    try:
        exec(x)
    except (SyntaxError, ZeroDivisionError):
        print ("WARNING: Invalid Equation")
    else:
        z = x
        print(x)

刚刚添加了

z = x

并用z

更改“_”

谢谢！

Answer 1

def ans():
        try:
            return _
    except NameError:
        return 0 # appropriate value

你的尝试，除了需要有相同的缩进。像这样使用它

def ans():
    try:
        return _
    except NameError:
        return 0 # appropriate value

Answer 2

valid_chars = list("0123456789-+/* \n")
while True:
    x = "ans = "
    y = raw_input(" >> ")
    x += y
    if any(c not in valid_chars for c in y.replace('ans','')):
        print("WARNING: Invalid Equation")
        continue
    try:
        exec(x)
    except (SyntaxError, ZeroDivisionError):
        print ("WARNING: Invalid Equation")
    except NameError:
        if y == 'ans':
            print("ans undefined")
        else:
            raise
    else:
        print(ans)

如何让用户重用python计算器中先前计算的结果

2 个答案: