5.1. Unpack GetItem¶
Allows to get element from ordered sequence
Works with ordered sequences:
str,list,tuple
5.1.1. Syntax¶
Index must
int(positive, negative or zero)Positive Index starts with
0Negative index starts with
-1
>>> data = ['a', 'b', 'c']
>>>
>>> data[0]
'a'
>>> data[1]
'b'
>>> data[-1]
'c'
5.1.2. Positive Index¶
Starts with
0Index must be less than length of an object
Ascending
>>> data = ['a', 'b', 'c']
>>>
>>> data[0]
'a'
>>> data[1]
'b'
>>> data[2]
'c'
>>>
>>> data[3]
Traceback (most recent call last):
IndexError: list index out of range
5.1.3. Negative Index¶
0is equal to-0Starts with
-1Descending
Negative index starts from the end and go right to left
>>> data = ['a', 'b', 'c']
>>>
>>> data[-0]
'a'
>>> data[-1]
'c'
>>> data[-2]
'b'
>>> data[-3]
'a'
>>>
>>> data[-4]
Traceback (most recent call last):
IndexError: list index out of range
>>> -0 == 0
True
5.1.4. Index Type¶
Index must int (positive, negative or zero)
>>> data[1.1]
Traceback (most recent call last):
TypeError: list indices must be integers or slices, not float
5.1.5. Getitem from str¶
Get Item from str:
>>> data = 'abc'
>>>
>>> data[0]
'a'
>>> data[1]
'b'
>>> data[2]
'c'
>>> data[-0]
'a'
>>> data[-1]
'c'
>>> data[-2]
'b'
5.1.6. Getitem from list¶
GetItem from list:
>>> data = ['a', 'b', 'c']
>>>
>>> data[0]
'a'
>>> data[1]
'b'
>>> data[2]
'c'
>>> data[-0]
'a'
>>> data[-1]
'c'
>>> data[-2]
'b'
5.1.7. Getitem from tuple¶
>>> data = ('a', 'b', 'c')
>>>
>>> data[0]
'a'
>>> data[1]
'b'
>>> data[2]
'c'
>>> data[-0]
'a'
>>> data[-1]
'c'
>>> data[-2]
'b'
5.1.8. Getitem from set¶
GetItem from set is impossible. set is unordered data structure:
>>> data = {'a', 'b', 'c', 'd'}
>>>
>>> data[0]
Traceback (most recent call last):
TypeError: 'set' object is not subscriptable
>>> data[1]
Traceback (most recent call last):
TypeError: 'set' object is not subscriptable
>>> data[2]
Traceback (most recent call last):
TypeError: 'set' object is not subscriptable
>>> data[-0]
Traceback (most recent call last):
TypeError: 'set' object is not subscriptable
>>> data[-1]
Traceback (most recent call last):
TypeError: 'set' object is not subscriptable
>>> data[-2]
Traceback (most recent call last):
TypeError: 'set' object is not subscriptable
5.1.9. Getitem from list[list]¶
Get elements from list of list:
>>> data = [[1, 2, 3],
... [4, 5, 6],
... [7, 8, 9]]
...
>>> data[0][0]
1
>>> data[0][1]
2
>>> data[0][2]
3
>>> data[1][0]
4
>>> data[1][1]
5
>>> data[1][2]
6
>>> data[2][0]
7
>>> data[2][1]
8
>>> data[2][2]
9
5.1.10. Getitem from list[tuple]¶
Get elements from list of tuple:
>>> data = [
... (4.7, 3.2, 1.3, 0.2, 'setosa'),
... (7.0, 3.2, 4.7, 1.4, 'versicolor'),
... (7.6, 3.0, 6.6, 2.1, 'virginica')]
...
>>> data[0]
(4.7, 3.2, 1.3, 0.2, 'setosa')
>>> data[0][0]
4.7
>>> data[0][4]
'setosa'
>>> data[1]
(7.0, 3.2, 4.7, 1.4, 'versicolor')
>>> data[1][0]
7.0
>>> data[1][4]
'versicolor'
>>> data[2]
(7.6, 3.0, 6.6, 2.1, 'virginica')
>>> data[2][0]
7.6
>>> data[2][4]
'virginica'
5.1.11. Getitem from list[Sequence]¶
Get elements from list of sequences:
>>> data = [[1, 2, 3],
... (4, 5, 6),
... {7, 8, 9}]
...
>>> data[0]
[1, 2, 3]
>>> data[0][0]
1
>>> data[0][1]
2
>>> data[0][2]
3
>>> data[1]
(4, 5, 6)
>>> data[1][0]
4
>>> data[1][1]
5
>>> data[1][2]
6
>>> data[2] == {7, 8, 9}
True
>>> data[2][0]
Traceback (most recent call last):
TypeError: 'set' object is not subscriptable
5.1.12. Assignments¶
"""
* Assignment: Iterable GetItem Header
* Required: yes
* Complexity: easy
* Lines of code: 1 lines
* Time: 3 min
English:
1. Define `result: tuple[str]`
2. Select header from `DATA` (row with index 0)
3. Write header to `result`
4. Non-functional requirements:
a. Use only indexes (`getitem`)
b. Do not use `str.split()`, `slice`, `for`, `while` or any other
control-flow statement
5. Run doctests - all must succeed
Polish:
1. Zdefiniuj `result: tuple[str]`
2. Wybierz nagłówek z `DATA` (wiersz o indeksie 0)
3. Zapisz nagłówek do `result`
4. Wymagania niefunkcjonalne:
a. Korzystaj tylko z indeksów (`getitem`)
b. Nie używaj `str.split()`, `slice`, `for`, `while` lub
jakiejkolwiek innej instrukcji sterującej
5. Uruchom doctesty - wszystkie muszą się powieść
Tests:
>>> import sys; sys.tracebacklimit = 0
>>> assert result is not Ellipsis, \
'Assign your result to variable `result`'
>>> assert type(result) is tuple, \
'Variable `result` has invalid type, should be tuple'
>>> assert len(result) == 5, \
'Variable `result` length should be 5'
>>> result
('sepal_length', 'sepal_width', 'petal_length', 'petal_width', 'species')
"""
DATA = [
('sepal_length', 'sepal_width', 'petal_length', 'petal_width', 'species'),
(5.8, 2.7, 5.1, 1.9, 'virginica'),
(5.1, 3.5, 1.4, 0.2, 'setosa'),
(5.7, 2.8, 4.1, 1.3, 'versicolor'),
(6.3, 2.9, 5.6, 1.8, 'virginica'),
(6.4, 3.2, 4.5, 1.5, 'versicolor'),
(4.7, 3.2, 1.3, 0.2, 'setosa'),
]
# Header from `DATA` (row with index 0)
# type: tuple[str]
result = ...
"""
* Assignment: Iterable GetItem Positive
* Required: yes
* Complexity: easy
* Lines of code: 3 lines
* Time: 3 min
English:
1. Define `result_a: tuple` with row from `DATA` at index 2
2. Define `result_b: tuple` with row from `DATA` at index 4
3. Define `result_c: tuple` with row from `DATA` at index 6
4. Non-functional requirements:
a. Use only indexes (`getitem`)
b. Do not use `str.split()`, `slice`, `for`, `while` or any other
control-flow statement
5. Run doctests - all must succeed
Polish:
1. Zdefiniuj `result_a: tuple` z wierszem z `DATA` o indeksie 2
2. Zdefiniuj `result_b: tuple` z wierszem z `DATA` o indeksie 4
3. Zdefiniuj `result_c: tuple` z wierszem z `DATA` o indeksie 6
4. Wymagania niefunkcjonalne:
a. Korzystaj tylko z indeksów (`getitem`)
b. Nie używaj `str.split()`, `slice`, `for`, `while` lub
jakiejkolwiek innej instrukcji sterującej
5. Uruchom doctesty - wszystkie muszą się powieść
Tests:
>>> import sys; sys.tracebacklimit = 0
>>> assert result_a is not Ellipsis, \
'Assign your result to variable `result_a`'
>>> assert result_b is not Ellipsis, \
'Assign your result to variable `result_b`'
>>> assert result_c is not Ellipsis, \
'Assign your result to variable `result_c`'
>>> assert type(result_a) is tuple, \
'Variable `result_a` has invalid type, should be tuple'
>>> assert type(result_b) is tuple, \
'Variable `result_b` has invalid type, should be tuple'
>>> assert type(result_c) is tuple, \
'Variable `result_c` has invalid type, should be tuple'
>>> assert len(result_a) == 5, \
'Variable `result_a` length should be 5'
>>> assert len(result_b) == 5, \
'Variable `result_b` length should be 5'
>>> assert len(result_c) == 5, \
'Variable `result_c` length should be 5'
>>> result_a
(5.1, 3.5, 1.4, 0.2, 'setosa')
>>> result_b
(6.3, 2.9, 5.6, 1.8, 'virginica')
>>> result_c
(4.7, 3.2, 1.3, 0.2, 'setosa')
"""
DATA = [
('sepal_length', 'sepal_width', 'petal_length', 'petal_width', 'species'),
(5.8, 2.7, 5.1, 1.9, 'virginica'),
(5.1, 3.5, 1.4, 0.2, 'setosa'),
(5.7, 2.8, 4.1, 1.3, 'versicolor'),
(6.3, 2.9, 5.6, 1.8, 'virginica'),
(6.4, 3.2, 4.5, 1.5, 'versicolor'),
(4.7, 3.2, 1.3, 0.2, 'setosa'),
]
# Row from `DATA` at index 2
# type: tuple[float|str]
result_a = ...
# Row from `DATA` at index 4
# type: tuple[float|str]
result_b = ...
# Row from `DATA` at index 6
# type: tuple[float|str]
result_c = ...
"""
* Assignment: Iterable GetItem Negative
* Required: yes
* Complexity: easy
* Lines of code: 3 lines
* Time: 3 min
English:
1. Define `result_a: tuple` with row from `DATA` at index -5
2. Define `result_b: tuple` with row from `DATA` at index -3
3. Define `result_c: tuple` with row from `DATA` at index -1
4. Non-functional requirements:
a. Use only indexes (`getitem`)
b. Do not use `str.split()`, `slice`, `for`, `while` or any other
control-flow statement
5. Run doctests - all must succeed
Polish:
1. Zdefiniuj `result_a: tuple` z wierszem z `DATA` o indeksie -5
2. Zdefiniuj `result_b: tuple` z wierszem z `DATA` o indeksie -3
3. Zdefiniuj `result_c: tuple` z wierszem z `DATA` o indeksie -1
4. Wymagania niefunkcjonalne:
a. Korzystaj tylko z indeksów (`getitem`)
b. Nie używaj `str.split()`, `slice`, `for`, `while` lub
jakiejkolwiek innej instrukcji sterującej
5. Uruchom doctesty - wszystkie muszą się powieść
Tests:
>>> import sys; sys.tracebacklimit = 0
>>> assert result_a is not Ellipsis, \
'Assign your result to variable `result_a`'
>>> assert result_b is not Ellipsis, \
'Assign your result to variable `result_b`'
>>> assert result_c is not Ellipsis, \
'Assign your result to variable `result_c`'
>>> assert type(result_a) is tuple, \
'Variable `result_a` has invalid type, should be tuple'
>>> assert type(result_b) is tuple, \
'Variable `result_b` has invalid type, should be tuple'
>>> assert type(result_c) is tuple, \
'Variable `result_c` has invalid type, should be tuple'
>>> assert len(result_a) == 5, \
'Variable `result_a` length should be 5'
>>> assert len(result_b) == 5, \
'Variable `result_b` length should be 5'
>>> assert len(result_c) == 5, \
'Variable `result_c` length should be 5'
>>> result_a
(5.1, 3.5, 1.4, 0.2, 'setosa')
>>> result_b
(6.3, 2.9, 5.6, 1.8, 'virginica')
>>> result_c
(4.7, 3.2, 1.3, 0.2, 'setosa')
"""
DATA = [
('sepal_length', 'sepal_width', 'petal_length', 'petal_width', 'species'),
(5.8, 2.7, 5.1, 1.9, 'virginica'),
(5.1, 3.5, 1.4, 0.2, 'setosa'),
(5.7, 2.8, 4.1, 1.3, 'versicolor'),
(6.3, 2.9, 5.6, 1.8, 'virginica'),
(6.4, 3.2, 4.5, 1.5, 'versicolor'),
(4.7, 3.2, 1.3, 0.2, 'setosa'),
]
# Row from `DATA` at index -5
# type: tuple[float|str]
result_a = ...
# Row from `DATA` at index -3
# type: tuple[float|str]
result_b = ...
# Row from `DATA` at index -1
# type: tuple[float|str]
result_c = ...
"""
* Assignment: Iterable GetItem Select
* Required: yes
* Complexity: easy
* Lines of code: 4 lines
* Time: 5 min
English:
1. Create `result: list`
a. Append to `result` a row from `DATA` at index 2
b. Append to `result` a row from `DATA` at index 4
c. Append to `result` a row from `DATA` at index -2
2. Non-functional requirements:
a. Use only indexes (`getitem`)
b. Do not use `str.split()`, `slice`, `for`, `while` or any other
control-flow statement
3. Run doctests - all must succeed
Polish:
1. Stwórz `result: list`
a. Dodaj do `result` wiersz z `DATA` o indeksie 2
b. Dodaj do `result` wiersz z `DATA` o indeksie 4
c. Dodaj do `result` wiersz z `DATA` o indeksie -2
2. Wymagania niefunkcjonalne:
a. Korzystaj tylko z indeksów (`getitem`)
b. Nie używaj `str.split()`, `slice`, `for`, `while` lub
jakiejkolwiek innej instrukcji sterującej
3. Uruchom doctesty - wszystkie muszą się powieść
Hints:
* `list.append()`
Tests:
>>> import sys; sys.tracebacklimit = 0
>>> assert result is not Ellipsis, \
'Assign your result to variable `result`'
>>> assert type(result) is list, \
'Variable `result` has invalid type, should be list'
>>> assert len(result) == 3, \
'Variable `result` length should be 6'
>>> result # doctest: +NORMALIZE_WHITESPACE
[(5.1, 3.5, 1.4, 0.2, 'setosa'),
(6.3, 2.9, 5.6, 1.8, 'virginica'),
(6.4, 3.2, 4.5, 1.5, 'versicolor')]
"""
DATA = [
('sepal_length', 'sepal_width', 'petal_length', 'petal_width', 'species'),
(5.8, 2.7, 5.1, 1.9, 'virginica'),
(5.1, 3.5, 1.4, 0.2, 'setosa'),
(5.7, 2.8, 4.1, 1.3, 'versicolor'),
(6.3, 2.9, 5.6, 1.8, 'virginica'),
(6.4, 3.2, 4.5, 1.5, 'versicolor'),
(4.7, 3.2, 1.3, 0.2, 'setosa'),
]
# Empty list
# type: list[list|tuple|set]
result = ...
# Append row from DATA at index 2
...
# Append row from DATA at index 4
...
# Append row from DATA at index -2
...
"""
* Assignment: Iterable GetItem Header/Data
* Required: yes
* Complexity: easy
* Lines of code: 11 lines
* Time: 5 min
English:
1. Separate header (first line) from data:
a. Define `header: tuple[str]` with header
b. Define `data: list[tuple]` with other data without header
2. Non-functional requirements:
a. Use only indexes (`getitem`)
b. Do not use `str.split()`, `slice`, `for`, `while` or any other
control-flow statement
c. You can use copy and paste and/or vertical select `alt`
3. Run doctests - all must succeed
Polish:
1. Odseparuj nagłówek (pierwsza linia) od danych:
a. Zdefiniuj `header: tuple[str]` z nagłówkiem
b. Zdefiniuj `data: list[tuple]` z danymi bez nagłówka
2. Wymagania niefunkcjonalne:
a. Korzystaj tylko z indeksów (`getitem`)
b. Nie używaj `str.split()`, `slice`, `for`, `while` lub
jakiejkolwiek innej instrukcji sterującej
c. Możesz użyć kopiowania i wklejania lub/i zaznaczania pioniwego `alt`
3. Uruchom doctesty - wszystkie muszą się powieść
Hints:
* `list.append()`
Tests:
>>> import sys; sys.tracebacklimit = 0
>>> assert header is not Ellipsis, \
'Assign your result to variable `header`'
>>> assert data is not Ellipsis, \
'Assign your result to variable `data`'
>>> assert type(header) is tuple, \
'Variable `header` has invalid type, should be tuple'
>>> assert all(type(x) is tuple for x in data), \
'All elements in `data` should be tuple'
>>> assert header not in data, \
'Header should not be in `data`'
>>> header
('sepal_length', 'sepal_width', 'petal_length', 'petal_width', 'species')
>>> data # doctest: +NORMALIZE_WHITESPACE
[(5.8, 2.7, 5.1, 1.9, 'virginica'),
(5.1, 3.5, 1.4, 0.2, 'setosa'),
(5.7, 2.8, 4.1, 1.3, 'versicolor'),
(6.3, 2.9, 5.6, 1.8, 'virginica'),
(6.4, 3.2, 4.5, 1.5, 'versicolor'),
(4.7, 3.2, 1.3, 0.2, 'setosa')]
"""
DATA = [
('sepal_length', 'sepal_width', 'petal_length', 'petal_width', 'species'),
(5.8, 2.7, 5.1, 1.9, 'virginica'),
(5.1, 3.5, 1.4, 0.2, 'setosa'),
(5.7, 2.8, 4.1, 1.3, 'versicolor'),
(6.3, 2.9, 5.6, 1.8, 'virginica'),
(6.4, 3.2, 4.5, 1.5, 'versicolor'),
(4.7, 3.2, 1.3, 0.2, 'setosa'),
]
# Row at index 0 from DATA
# type: tuple[str]
header = ...
# Rows at all the other indexes from DATA (use only getitem)
# type: list[tuple]
data = ...