下面是一个使用locals()函数判断变量是否已定义的示例代码: defcheck_variable_defined():variable_name='x'ifvariable_nameinlocals():print(variable_name,'is defined')else:print(variable_name,'is not defined')check_variable_defined() 1. 2. 3. 4. 5. 6. 7. 8. 以上代码中,我们定义了一个函数c...
2 is a prime number 3 is a prime number 4 equals 2 * 2 5 is a prime number 6 equals 2 * 3 7 is a prime number 8 equals 2 * 4 9 equals 3 * 3 (是的,这是正确的代码,仔细一看:该else条款属于for循环,不是的if。陈述) 当循环使用,该else条款有更多的共同点与 else一个条款try声明...
Then it’s easy to test whether a variable is bound toNone: if x is None: some_fallback_operation( ) else: some_operation(x) Discussion Python doesn’t have a specific function to test whether a variable is defined, since all variables are expected to have been defined before use, even...
以下虚拟示例演示 Python 具有动态类型: >>>ifFalse:...1+"two"# This line never runs, so no TypeError is raised...else:...1+2...3>>>1+"two"# Now this is type checked, and a TypeError is raisedTypeError:unsupportedoperandtype(s)for+:'int'and'str' 在第一个示例中,分支1 + "two"...
But when we want to check if the variable is a string, is the operator is more appropriate. For a more detailed explanation of when to use one or the other, check this article. == is slower: python3 -m timeit -s "variable = 'hello_world'" "type(variable) == str" 5000000 loops...
I get error "local variable y defined in enclosing scope on line 7 referenced before assignment". How can I format this code so that when the function is first called, it uses the global variables, and then on each subsequent calling it uses the variable y it redefined?...
NameError: name 'lcl_var' is not defined We cannot use a local variable outside of the function it is assigned in. If we try to do so, we’ll receive aNameErrorin return. Let’s review another example where we use the same variable name for a global variable and a local variable:...
/* Number of items in variable part */ typedef struct { PyObject_VAR_HEAD } PyVarObject; 有关类型和对象更多的信息,将在后续章节中详述. 1.3 名字空间 名字空间是 Python 最核⼼心的内容. >>> x NameError: name 'x' is not defined 我们习惯于将 x 称为变量,但在这⾥里,更准确的词语是 ...
if ord(e) > 128: print("^ ", end='') else: print(' ', end='') print() s = "【a, b,中" find_chinese_char(s) s = "([10, 2,3,4】“])" find_chinese_char(s) 如果经常受困于这些错误,建议阅读代码里面的中、英文符号 - 知乎 (zhihu.com)。
Python变量作用域 if for 1、你的名字 我们先来审视一下模块。这是一个合适的尺度,由此展开,可以顺利地连接起函数与包。 模块是什么?任何以.py后缀结尾的文件就是一个模块(module)。 模块的好处是什么?首先,便于拆分不同功能的代码,单一功能的少量代码更容易维护;其次,便于组装与重复利用,Python 以丰富的第三方...