Scope of Variables

1. Scopeof Variables
 SCOPEmeans in which part(s) of the program, a
particular piece of code or data is accessible or
known.
 InPythonthere are broadly 2 kindsof Scopes:
Global Scope
Local Scope

2. Global Scope
 A name declared in top level segment( main ) of a
program is said to have global scope and can be
usedin entire program.
 Variable defined outside all functions are global
variables.

3. Local Scope
 A name declare in a function body is said to have
local scope i.e. it can be used only within this
function and the other block inside the function.
 Theformal parameters are also having local scope.
 Letusunderstandwithexample….

4. Example– Localand Global Scope

5. Example– Localand Global Scope
„a‟isnot accessible
here becauseit is
declared in function
area(), soscopeis
local to area()

6. Example– Localand Global
Scope
Variable "ar‟ is accessible in
function showarea() because
it ishaving Global Scope

7. Thisdeclaration “global count” is
necessaryfor usingglobal
variables in function, other wise an
error “local variable 'count'
referenced before assignment”
will appear becauselocal scope
will create variable “count” and it
will be found unassigned

8. Lifetime of Variable
 Is the time for which a variable lives in memory. For
Global variables the lifetime isentire program run
i.e. as long as program is executing. For Local
variables lifetime is their function‟s run i.e. as long as
function isexecuting.

9. NameResolution(ScopeResolution)
 Forevery nameusedwithin program python follows nameresolutionrules
knownasLEGB rule.
 (i) LOCAL : first check whether name is in local environment, if yes
Python uses its value otherwise moves to (ii)
 (ii) ENCLOSING ENVIRONMENT: if not in local, Python checks whether
name is in Enclosing Environment, if yes Python uses its value
otherwise moves to (iii)
 GLOBAL ENVIRONMENT: if not in above scope Python checks it in
Global environment,if yes Python uses itotherwise moves to (iv)
 BUILT-IN ENVIRONMENT: if not in above scope, Python checks it in built-
in environment, if yes, Python uses its value otherwise Python would
reportthe error:
 name<variable> notdefined

10. Predict the output
Programwith
variable “value” in
both LOCALand
GLOBALSCOPE

11. Predict the output
Programwith
variable “value” in
both LOCALand
GLOBALSCOPE

12. Predict the output
UsingGLOBAL
variable “value” in
local scope

13. Predict the output
UsingGLOBAL
variable “value” in
local scope

14. Predict the output
Variable “value”
neither in local nor
global scope

15. Predict the output
Variable “value”
neither in local nor
global scope

16. Predict the output
Variable in Global
notin Local
(input in variable at
global scope)

17. Predict the output
Variable in Global
notin Local
(input in variable at
global scope)