检查是否存在多个变量的更简单方法？

Question

I know a way how to check if one variable exists:

try:
    my_var
except NameError:
    # not exist

I need to check for existence of many variables and make an action only if all of them exist. Writing a chain of try..except or wrapping a few try..except 's one around another looks rather ugly. Is there any nice way to check many vars?

Answer 1

If there is no way around, you can check the return value of dir() . sets might come in handy.

a = 1
b = 2
d = 3

set_vars = {'a', 'b', 'c', 'd'} # declare the variable names to check for
set_vars_exist = set_vars.intersection(set(dir()))
all_vars_exist = set_vars_exist == set_vars

print(all_vars_exist)
# False, because c is missing

Be aware that there might be some pathological edge case (depending on the output of dir() ) where this code fails.