在python中声明一个全局动态变量

Question

我是一个python /编程新手，也许我的问题根本就没有意义。

我的问题是，如果变量是动态的，我无法将变量变为全局变量，我的意思是我可以这样做：

def creatingShotInstance():

    import movieClass

    BrokenCristals = movieClass.shot()
    global BrokenCristals #here I declare BrokenCristals like a global variable and it works, I have access to this variable (that is a  shot class instance) from any part of my script.
    BrokenCristals.set_name('BrokenCristals')
    BrokenCristals.set_description('Both characters goes through a big glass\nand break it')
    BrokenCristals.set_length(500)
    Fight._shots.append(BrokenCristals)

def accesingShotInstance():
    import movieClass

    return BrokenCristals.get_name()#it returns me 'BrokenCristals'

但如果不是这样做，我会声明一个像这样的字符串变量：

def creatingShotInstance():

    import movieClass

    a = 'BrokenCristals'

    vars()[a] = movieClass.shot()
    global a #this line is the only line that is not working now, I do not have acces to BrokenCristals class instance from other method, but I do have in the same method.
    eval(a+".set_name('"+a+"')")
    eval(a+".set_description('Both characters goes through a big glass\nand break it')")
    eval(a+".set_length(500)")
    Fight._shots.append(vars()[a])

def accesingShotInstance():
    import movieClass

    return BrokenCristals.get_name()#it returns me 'BrokenCristals is not defined'

我试过了：

global vars()[a]

和此：

global eval(a)

但它给了我一个错误。我该怎么办？

Answer 1

为了完整起见，这是您原始问题的答案。但这几乎肯定不是你想要做的事情 - 很少有情况下修改范围的dict是正确的。

globals()[a] = 'whatever'

Answer 2

使用dict：

而不是动态全局变量

movies = {}

a = 'BrokenCristals'

movies[a] = movieClass.shot()
movies[a].set_name(a)
# etc

Answer 3

global关键字指定您在一个范围内使用的变量实际上属于外部范围。由于您的示例中没有嵌套作用域，因此global不知道您要执行的操作。见Using global variables in a function other than the one that created them

Answer 4

您的代码运行良好！

这只是拼写错误和缺少括号！

第一个语法错误没有方括号：

  File "main.py", line 6
    global BrokenCristals
    ^
SyntaxError: name 'BrokenCristals' is assigned to before global declaration

第二个语法错误 global 末尾没有字母 s：

  File "main.py", line 6
    global [BrokenCristals]
           ^
SyntaxError: invalid syntax

更正的语法：

def creatingShotInstance():

    import movieClass

    BrokenCristals = movieClass.shot()
    globals [BrokenCristals]
    BrokenCristals.set_name('BrokenCristals')
    BrokenCristals.set_description('Both characters goes through a big glass\nand break it')
    BrokenCristals.set_length(500)
    Fight._shots.append(BrokenCristals)

def accesingShotInstance():
    import movieClass

    return BrokenCristals.get_name()

使用声明的字符串修正语法：

def creatingShotInstance():

    import movieClass

    a = 'BrokenCristals'

    vars()[a] = movieClass.shot()
    globals [a] 
    eval(a+".set_name('"+a+"')")
    eval(a+".set_description('Both characters goes through a big glass\nand break it')")
    eval(a+".set_length(500)")
    Fight._shots.append(vars()[a])

def accesingShotInstance():
    import movieClass

    return BrokenCristals.get_name()