MISC

MISC

Let’s Do Digital Team

Mutability

• Mutability is the ability of a variable to be changed.
• As strange as it sounds, in python, some variables cannot be changed.
• If you update an immutable variable, the variable is created again from scratch.

Mutability

• Immutable variables include:
  • booleans
  • integers
  • floats
  • strings
  • tuples

Mutability

• Don’t trust me? Try this:

immutable_integer.py

x = 10

print(id(x))

x = 6

print(id(x))

Output

    4463277792
    4463277952

Mutable variables

• And a list of mutable variable types include:
  • lists
  • dictionaries
  • classes

Scope

• In most programming languages, a variable has scope.
• Scope defines where a variable can be read and altered.
• Scope is determined by where a variable is originally defined.

Scope example

scope.py

def patient_info():
    patient_name = "Alice Smith"
    print(f"Patient Name: {patient_name}")

patient_info()
print(patient_name)

Output

    Patient Name: Alice Smith
    Traceback (most recent call last):
        File "/scope.py", line 6, in <module>
            print(patient_name)
                  ^^^^^^^^^^^^
    NameError: name 'patient_name' is not defined.

Global keyword

• To make a variable accessible inside your function or class, you can use the global keyword.
• Using global allows you to reassign any variable.
• Technically you do not need to use global if you are only updating (eg adding elements) mutable variables (eg lists and dictionaries).

Scope example - global

global.py

patient_name = ""

def patient_info():
    global patient_name
    patient_name = "Alice Smith"
    print(f"Patient Name: {patient_name}")

patient_info()
print(patient_name)

Output

    Patient Name: Alice Smith
    Alice Smith