python - 如何检查变量是否存在？(How do I check if a variable exists?)

Question

I want to check if a variable exists.

(我想检查一个变量是否存在。)

Now I'm doing something like this:

(现在我正在做这样的事情：)

try:
   myVar
except NameError:
   # Do something.

Are there other ways without exceptions?

(是否有其他方法无一例外？)

  ask by Max Frai translate from so

Answer 1

To check the existence of a local variable:

(要检查是否存在局部变量：)

if 'myVar' in locals():
  # myVar exists.

To check the existence of a global variable:

(要检查是否存在全局变量：)

if 'myVar' in globals():
  # myVar exists.

To check if an object has an attribute:

(要检查对象是否具有属性：)

if hasattr(obj, 'attr_name'):
  # obj.attr_name exists.