In Python 2, how do I write to variable in the parent scope?

Question

I have the following code inside a function:

stored_blocks = {}
def replace_blocks(m):
    block = m.group(0)
    block_hash = sha1(block)
    stored_blocks[         


        

Answer 1

Using the global keyword is fine. If you write:

num_converted = 0
def convert_variables(m):
    global num_converted
    name = m.group(1)
    num_converted += 1
    return '<%%= %s %%>' % name

... num_converted doesn't become a "global variable" (i.e. it doesn't become visible in any other unexpected places), it just means it can be modified inside convert_variables. That seems to be exactly what you want.

To put it another way, num_converted is already a global variable. All the global num_converted syntax does is tell Python "inside this function, don't create a local num_converted variable, instead, use the existing global one.