Scope

Question 1

what is scope

Answer 1

scope dictates whether or not a variable/function is available in certain parts of the program
- scope rules apply to module/variable/function identifiers

Question 2

Global scope

Answer 2

• usable anywhere in the program

- use is discouraged

Question 3

problems with global scope

Answer 3

• many issues in large programs due to # of functions and modules which could change them
• if statements could change global variables accidentally
• programmer error

Question 4

global variable restrictions

Answer 4

1. can get value of global variable inside a function

2. cannot give new value to a global variable inside a function unlesss using global keyword

Question 5

Constant identifiers

Answer 5

• for example PI, a value that will not change
• typically styled with all caps
• python doesn’t have constant, so instead create global variable with all caps

Question 6

Important GV notes

Answer 6

• python has a list of special variables

- not really different from global scope but handled by python instead of programmer

Question 7

local scope

Answer 7

• variable in a function, therefore its scope is limited to the function
• can have same name as global variable but are different entitites
• function parameters all have local scope

Question 8

ID()

Answer 8

use to test if variables are aliases

Question 9

Important list/dict scope

Answer 9

1. if necessary to make a list/dict inside a function don’t reuse name
2. change elements as needed but keep in mind when using list/dict as a parameter it is an alias of the argument so change content of parameter is to change the argument