Print all local variables accessible to the current scope in Lua

Question

I know how to print "all" global variables using the following code

for k,v in pairs(_G) do     print("Global key", k, "value", v) end 

So my question is how to do that for all variables that are accessible from the currently executing function, something that can do what locals() does for Python.

Answer 1

Use debug.getlocal.

Answer 2

Here is an implementation of a locals() function. It will return a table of locals from the calling scope:

function locals()   local variables = {}   local idx = 1   while true do     local ln, lv = debug.getlocal(2, idx)     if ln ~= nil then       variables[ln] = lv     else       break     end     idx = 1 + idx   end   return variables end 

Notice that in the lua REPL, each line is a separate chunk with separate locals. Also, internal variables are returned (names start with '(' if you want to remove them):

> local a = 2; for x, v in pairs(locals()) do print(x, v) end a   2 (*temporary)    function: 0x10359b38 

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Thanks for the accept. You have unlocked the last piece of the puzzle! ;-)

Upvalues are local variables from outer scopes, that are used in the current function. They are neither in _G nor in locals()

function upvalues()   local variables = {}   local idx = 1   local func = debug.getinfo(2, "f").func   while true do     local ln, lv = debug.getupvalue(func, idx)     if ln ~= nil then       variables[ln] = lv     else       break     end     idx = 1 + idx   end   return variables end 

Example (notice you have to use a for it to show up):

> local a= 2; function f() local b = a; for x,v in pairs(upvalues()) do print(x,v) end end; f() a   2