Question

以下是我的节目的摘录：

weaponinput = input("Would you like a rifle, a pistol, or a shotgun?")
if weaponinput == " pistol":
    weapon = (int(pistol_1))
if weaponinput == " rifle":
    weapon = (int(rifle_1))
if weaponinput == " shotgun":
    weapon = (int(shotgun_1))
if weaponinput != (" shotgun") or (" rifle") or (" pistol") or (" sniper rifle"):
    print("In your futile attempt to turn",weaponinput,"into a weapon you accidentally blow your brains accross the ground.")

if子句始终在第8行触发，无论weaponinput的值如何。为什么会这样？我正在使用python，并没有真正理解许多其他语言

Answer 1

您已写过相当于

的内容

if (w != 1) or (2) or (3):
 print("something")

(2)非零，因此为True。在您的代码中("rifle")不是None，因此是True。

正确的表格是

if (w != 1) or (w!=2) or (w!=3):
    ...

另一种方法可能是

if weaponinput == "rifle:
    ...
elif weaponinput == "pistol": 
     ...
else:
    print("bad input message")

另一种方式：

WeaponCodes = {"pistol":int(pistol1), "rifle":int(rifle1), ... }
try:
   weapon = WeaponCodes[weaponinput]
except KeyError:
   print("bad input message")

Answer 2

您需要将该行更改为以下内容：

if weaponinput != " shotgun" or weaponinput != " rifle" or weaponinput != " pistol" or weaponinput != " sniper rifle":

Answer 3

Pythonic将是：

if weaponinput not in (" shotgun", " rifle", " pistol", " sniper rifle"):
    print(...)

Answer 4

要检查多个条件，您必须将输入变量与所需条件进行比较，如：

if var <conditional operator1> condition1 <logical operator> var <conditional operator2> condition2等等。

所以在你的情况下，第8行必须是： if weaponinput != " shotgun" or weaponinput != " rifle" or weaponinput != " pistol" or weaponinput != " sniper rifle":

Answer 5

在所有运算符中，逻辑运算符（or，and和not）的优先级最低（Python Operator Precedence）。

在Python中，非空字符串的布尔值始终为true。

因此，您编写的代码相当于： -

weaponinput = input("Would you like a rifle, a pistol, or a shotgun?")
if weaponinput == " pistol":
    weapon = (int(pistol_1))
if weaponinput == " rifle":
    weapon = (int(rifle_1))
if weaponinput == " shotgun":
    weapon = (int(shotgun_1))
if weaponinput != (" shotgun") or True or True or True:
    print("In your futile attempt to turn",weaponinput,"into a weapon you accidentally blow your brains accross the ground.")

因此，无论weaponinput是否等于" shotgun“，第8行中的条件始终为真（因为or如果其操作数的至少一个是dos2unix <file>，则总是求值为真是的。

为什么我的程序总是会触发？

5 个答案: