Variable Scope for Scripts

[QueenSvetlana]

I just came across the book Code Complete, 2nd Ed on amazon. It comes with a checklist to ensure you write maintainable code.

Under Chapter 10: General Issues In Using Variables
Other General Issues in Using Data (p. 17)

One of the points says:

Do all variables have the smallest scope possible?

When referring to variable scope, do they mean large scale applications and using classes to achieve encapsulation? Suppose I had a script that doesn't use classes, but a List and functions to do certain tasks, example, a backup script:

def read_data_from_file(file_to_read):
    #code to read from file and build list
    return list_of_files

def copy_files_to_backup_folder(file_to_copy):
    #code to copy files

file_name="some/path/to/file"
files_to_backup = read_data_from_file(file_name)

for f in files_to_backup:
    copy_files_to_backup_folder(f)

Do you have to worry about variable scope when writing scripts for common admin tasks? In this case file_name?

How would you properly declare it to limit the variable scope as suggested by the checklist/book?

When should you worry about variable scope?