2.4. Type None¶

2.4.1. Type Definition¶

First letter capitalized, other are lower cased

Empty (null) or unknown (unset) value

It is not False value

With if statements behaves like negative values

Listing 2.14. NoneType Type Definition¶

data = None

2.4.2. Comparison¶

Do not use == or != to check None values (it works, but you shouldn't)

x is None - x is the same object as y

x is not None - x is not the same object as y

Listing 2.15. Do not use == or != to check None values (it works, but you shouldn't)¶

age = None

age == None             # True
age != None             # False

Listing 2.16. Use identity checking for None values¶

age = None

age is None             # True
age is not None         # False

2.4.3. Assignments¶

2.4.3.1. Type None¶

Assignment name: Type None
Last update: 2020-10-01
Complexity level: easy
Lines of code to write: 5 lines
Estimated time of completion: 3 min
Solution: solution/type_none.py

English

Use data from "Input" section (see below)
What you need to put in expressions to get the expected outcome?
Compare result with "Output" section (see below)

Polish

Użyj danych z sekcji "Input" (patrz poniżej)
Co należy podstawić w wyrażeniach aby otrzymać wartość oczekiwaną?
Porównaj wyniki z sekcją "Output" (patrz poniżej)

Input

a = ... is None                                                                       # True
b = ... is not None                                                                   # False
c = bool(bool(...) is not bool(...)) == False                                         # True
d = (bool(bool(...) is not bool(...)) == False and bool(...))                         # False
e = (bool(bool(...) is not bool(...)) == False and bool(...)) and (... is not None)   # False

Output

print(a)    # True
print(b)    # False
print(c)    # True
print(d)    # False
print(e)    # False

The whys and wherefores

Defining variables
Type casting
Logic types

Todo

Create more assignments