5.1. Operators

5.1.1. Comparision

• == - eq (equals)

• != - ne (not-equals)

Listing 5.1. Comparing str

'Monty Python' == 'Python'      # False
'Monty Python' != 'Python'      # True

'Python' == 'Python'            # True
'Python' != 'Python'            # False

'python' == 'Python'            # False
'python' != 'Python'            # True

Listing 5.2. Comparing tuple

(1, 2, 3) == (1, 2)             # False
(1, 2, 3) != (1, 2)             # True

(1, 2) == (1, 2)                # True
(1, 2) == (2, 1)                # False

Listing 5.3. Comparing list

[1, 2, 3] == [1, 2]             # False
[1, 2, 3] != [1, 2]             # True

[1, 2] == [1, 2]                # True
[1, 2] == [2, 1]                # False

Listing 5.4. Comparing set

{1, 2, 3} == {1, 2}             # False
{1, 2, 3} != {1, 2}             # True

{1, 2} == {1, 2}                # True
{1, 2} == {2, 1}                # True

5.1.2. Contains

• in checks whether value is in sequence

• works with str, list, tuple, set, frozenset, dict

• Computational complexity for checking if sequence "contains":

  • O(n) - in str

  • O(n) - in list

  • O(n) - in tuple

  • O(1) - in set

  • O(1) - in frozenset

  • O(1) - in dict

• More information in Contains

Listing 5.5. list contains

data = 'abc'

'x' in data                      # False
'a' in data                      # True

'x' not in data                  # True
'a' not in data                  # False

Listing 5.6. list contains

data = [1, 2, 3]

0 in data                        # False
1 in data                        # True

0 not in data                    # True
1 not in data                    # False

Listing 5.7. tuple contains

data = (1, 2, 3)

0 in data                        # False
1 in data                        # True

0 not in data                    # True
1 not in data                    # False

Listing 5.8. set contains

data = {1, 2, 3}

0 in data                        # False
1 in data                        # True

0 not in data                    # True
1 not in data                    # False

Listing 5.9. frozenset contains

data = frozenset({1, 2, 3})

0 in data                        # False
1 in data                        # True

0 not in data                    # True
1 not in data                    # False

data = {
    'first_name': 'Jan',
    'last_name': 'Twardowski',
}

'first_name' in data            # True
'agency' in data                # False

'first_name' not in data        # False
'agency' not in data            # True

5.1.3. Operator Precedence

Table 5.1. Operator precedence

Operator	Description
lambda	Lambda expression
if, elif, else	Conditional expression
and	Boolean AND
or	Boolean OR
not x	Boolean NOT
in, not in, is, is not, <, <=, >, >=, !=, ==	Comparisons, including membership tests and identity tests
|	Bitwise OR
^	Bitwise XOR
&	Bitwise AND
<<, >>	Shifts
**	Exponentiation
*, @, /, //, %	Multiplication, matrix multiplication, division, floor division, remainder
+, -	Addition and subtraction
+x, -x, ~x	Positive, negative, bitwise NOT
await	Await expression
x[index], x[index:index], x(arguments...), x.attribute	Subscription, slicing, call, attribute reference
(expressions...), [expressions...], {key: value...}, {expressions...}	Binding or tuple display, list display, dictionary display, set display

5.1.4. Assignments

5.1.4.1. Is even number

• Complexity level: easy

• Lines of code to write: 5 lines

• Estimated time of completion: 5 min

• Solution: solution/conditional_operators_modulo.py

English

1. Read a number from user

2. User will pass only valid int

3. Number is even, when divided modulo (%) by 2 reminder equal to 0

4. Print whether number is odd

5. Do not use if statement

Polish

1. Wczytaj liczbę od użytkownika

2. Użytkownika poda tylko poprawne int

3. Liczba jest parzysta, gdy dzielona modulo (%) przez 2 ma resztę równą 0

4. Wypisz czy liczba jest nieparzysta

5. Nie używaj instrukcji if

The whys and wherefores

• Reading input from user

• Type casting

• Print formatting

• Numerical operators

Hints

• % has different meaning for int and str