8.5. Function Scope¶

8.5.1. Access Scope¶

Listing 8.16. Functions has access to global values¶

data = [1, 2, 3]

def add():
    return sum(data)

print(add())
# 6

print(data)
# [1, 2, 3]

Listing 8.17. Shadowing¶

data = [1, 2, 3]

def add():
    data = [10, 20, 30]
    return sum(data)

print(add())
# 60

print(data)
# [1, 2, 3]

Listing 8.18. Modify global, BAD PRACTICE!!¶

data = [1, 2, 3]

def add():
    global data
    data = [10, 20, 30]
    return sum(data)

print(add())
# 60

print(data)
# [10, 20, 30]

8.5.2. Global Scope¶

All variables in main program

Variables are available inside all functions

print(globals())
# {'__builtins__': {'ArithmeticError': <class 'ArithmeticError'>,
#                   'AssertionError': <class 'AssertionError'>,
#                   'AttributeError': <class 'AttributeError'>,
#                   'BaseException': <class 'BaseException'>,
#                   'BlockingIOError': <class 'BlockingIOError'>,
#                   'BrokenPipeError': <class 'BrokenPipeError'>,
#                   'BufferError': <class 'BufferError'>,
#                   'BytesWarning': <class 'BytesWarning'>,
#                   'ChildProcessError': <class 'ChildProcessError'>,
#                   'ConnectionAbortedError': <class 'ConnectionAbortedError'>,
#                   'ConnectionError': <class 'ConnectionError'>,
#                   'ConnectionRefusedError': <class 'ConnectionRefusedError'>,
#                   'ConnectionResetError': <class 'ConnectionResetError'>,
#                   'DeprecationWarning': <class 'DeprecationWarning'>,
#                   'EOFError': <class 'EOFError'>,
#                   'Ellipsis': Ellipsis,
#                   'EnvironmentError': <class 'OSError'>,
#                   'Exception': <class 'Exception'>,
#                   'False': False,
#                   'FileExistsError': <class 'FileExistsError'>,
#                   'FileNotFoundError': <class 'FileNotFoundError'>,
#                   'FloatingPointError': <class 'FloatingPointError'>,
#                   'FutureWarning': <class 'FutureWarning'>,
#                   'GeneratorExit': <class 'GeneratorExit'>,
#                   'IOError': <class 'OSError'>,
#                   'ImportError': <class 'ImportError'>,
#                   'ImportWarning': <class 'ImportWarning'>,
#                   'IndentationError': <class 'IndentationError'>,
#                   'IndexError': <class 'IndexError'>,
#                   'InterruptedError': <class 'InterruptedError'>,
#                   'IsADirectoryError': <class 'IsADirectoryError'>,
#                   'KeyError': <class 'KeyError'>,
#                   'KeyboardInterrupt': <class 'KeyboardInterrupt'>,
#                   'LookupError': <class 'LookupError'>,
#                   'MemoryError': <class 'MemoryError'>,
#                   'ModuleNotFoundError': <class 'ModuleNotFoundError'>,
#                   'NameError': <class 'NameError'>,
#                   'None': None,
#                   'NotADirectoryError': <class 'NotADirectoryError'>,
#                   'NotImplemented': NotImplemented,
#                   'NotImplementedError': <class 'NotImplementedError'>,
#                   'OSError': <class 'OSError'>,
#                   'OverflowError': <class 'OverflowError'>,
#                   'PendingDeprecationWarning': <class
#                   'PendingDeprecationWarning'>,
#                   'PermissionError': <class 'PermissionError'>,
#                   'ProcessLookupError': <class 'ProcessLookupError'>,
#                   'RecursionError': <class 'RecursionError'>,
#                   'ReferenceError': <class 'ReferenceError'>,
#                   'ResourceWarning': <class 'ResourceWarning'>,
#                   'RuntimeError': <class 'RuntimeError'>,
#                   'RuntimeWarning': <class 'RuntimeWarning'>,
#                   'StopAsyncIteration': <class 'StopAsyncIteration'>,
#                   'StopIteration': <class 'StopIteration'>,
#                   'SyntaxError': <class 'SyntaxError'>,
#                   'SyntaxWarning': <class 'SyntaxWarning'>,
#                   'SystemError': <class 'SystemError'>,
#                   'SystemExit': <class 'SystemExit'>,
#                   'TabError': <class 'TabError'>,
#                   'TimeoutError': <class 'TimeoutError'>,
#                   'True': True,
#                   'TypeError': <class 'TypeError'>,
#                   'UnboundLocalError': <class 'UnboundLocalError'>,
#                   'UnicodeDecodeError': <class 'UnicodeDecodeError'>,
#                   'UnicodeEncodeError': <class 'UnicodeEncodeError'>,
#                   'UnicodeError': <class 'UnicodeError'>,
#                   'UnicodeTranslateError': <class 'UnicodeTranslateError'>,
#                   'UnicodeWarning': <class 'UnicodeWarning'>,
#                   'UserWarning': <class 'UserWarning'>,
#                   'ValueError': <class 'ValueError'>,
#                   'Warning': <class 'Warning'>,
#                   'ZeroDivisionError': <class 'ZeroDivisionError'>,
#                   '_': <Recursion on dict with id=4575702144>,
#                   '__build_class__': <built-in function __build_class__>,
#                   '__debug__': True,
#                   '__doc__': 'Built-in functions, exceptions, and other '
#                              'objects.\n'
#                              '\n'
#                              "Noteworthy: None is the `nil' object;
#                              Ellipsis "
#                              "represents `...' in slices.",
#                   '__import__': <bound method ImportHookManager.do_import
#                   of <module '_pydev_bundle.pydev_import_hook.import_hook'>>,
#                   '__loader__': <class '_frozen_importlib.BuiltinImporter'>,
#                   '__name__': 'builtins',
#                   '__package__': '',
#                   '__spec__': ModuleSpec(name='builtins', loader=<class
#                   '_frozen_importlib.BuiltinImporter'>),
#                   'abs': <built-in function abs>,
#                   'all': <built-in function all>,
#                   'any': <built-in function any>,
#                   'ascii': <built-in function ascii>,
#                   'bin': <built-in function bin>,
#                   'bool': <class 'bool'>,
#                   'breakpoint': <built-in function breakpoint>,
#                   'bytearray': <class 'bytearray'>,
#                   'bytes': <class 'bytes'>,
#                   'callable': <built-in function callable>,
#                   'chr': <built-in function chr>,
#                   'classmethod': <class 'classmethod'>,
#                   'compile': <built-in function compile>,
#                   'complex': <class 'complex'>,
#                   'copyright': Copyright (c) 2001-2019 Python Software Foundation.,
#                   'delattr': <built-in function delattr>,
#                   'dict': <class 'dict'>,
#                   'dir': <built-in function dir>,
#                   'divmod': <built-in function divmod>,
#                   'enumerate': <class 'enumerate'>,
#                   'eval': <built-in function eval>,
#                   'exec': <built-in function exec>,
#                   'execfile': <function execfile at 0x1107e93b0>,
#                   'exit': Use exit() or Ctrl-D (i.e. EOF) to exit,
#                   'filter': <class 'filter'>,
#                   'float': <class 'float'>,
#                   'format': <built-in function format>,
#                   'frozenset': <class 'frozenset'>,
#                   'getattr': <built-in function getattr>,
#                   'globals': <built-in function globals>,
#                   'hasattr': <built-in function hasattr>,
#                   'hash': <built-in function hash>,
#                   'help': Type help() for interactive help, or help(
#                   object) for help about object.,
#                   'hex': <built-in function hex>,
#                   'id': <built-in function id>,
#                   'input': <built-in function input>,
#                   'int': <class 'int'>,
#                   'isinstance': <built-in function isinstance>,
#                   'issubclass': <built-in function issubclass>,
#                   'iter': <built-in function iter>,
#                   'len': <built-in function len>,
#                   'license': Type license() to see the full license text,
#                   'list': <class 'list'>,
#                   'locals': <built-in function locals>,
#                   'map': <class 'map'>,
#                   'max': <built-in function max>,
#                   'memoryview': <class 'memoryview'>,
#                   'min': <built-in function min>,
#                   'next': <built-in function next>,
#                   'object': <class 'object'>,
#                   'oct': <built-in function oct>,
#                   'open': <built-in function open>,
#                   'ord': <built-in function ord>,
#                   'pow': <built-in function pow>,
#                   'print': <built-in function print>,
#                   'property': <class 'property'>,
#                   'quit': Use quit() or Ctrl-D (i.e. EOF) to exit,
#                   'range': <class 'range'>,
#                   'repr': <built-in function repr>,
#                   'reversed': <class 'reversed'>,
#                   'round': <built-in function round>,
#                   'runfile': <function runfile at 0x110bb24d0>,
#                   'set': <class 'set'>,
#                   'setattr': <built-in function setattr>,
#                   'slice': <class 'slice'>,
#                   'sorted': <built-in function sorted>,
#                   'staticmethod': <class 'staticmethod'>,
#                   'str': <class 'str'>,
#                   'sum': <built-in function sum>,
#                   'super': <class 'super'>,
#                   'tuple': <class 'tuple'>,
#                   'type': <class 'type'>,
#                   'vars': <built-in function vars>,
#                   'zip': <class 'zip'>},
#  '__doc__': None,
#  '__file__': '<input>',
#  '__loader__': <_frozen_importlib_external.SourceFileLoader object at
#  0x100dea9d0>,
#  '__name__': '__main__',
#  '__package__': None,
#  '__spec__': None}

8.5.3. Local Scope¶

Variables defined inside function

Variables are not available from outside

If outside the function, will return the same as globals()

print(locals())
# {...}

def echo():
    a = 1
    print(locals())

echo()
# {'a': 1}

def echo(a, b=2):
    c = 3
    print(locals())

echo(1)
# {'a':1, 'b':2, 'c':3}

8.5.4. Assignments¶

8.5.4.1. Function Scope Filter¶

Complexity level: easy
Lines of code to write: 5 lines
Estimated time of completion: 5 min
Solution: solution/function_scope_filter.py

English

Use data from "Input" section (see below)
Separate header from data
Define select: Set[str] with values 'setosa' and 'versicolor'
Iterate over data and split row into features and label (last)
Define function sum_if(features, label)
Function sums features, only when label is in select
When label is not in select return 0 (zero)
Print sum
Compare result with "Output" section (see below)

Polish

Użyj danych z sekcji "Input" (patrz poniżej)
Oddziel nagłówek od danych
Zdefiniuj select: Set[str] z wartościami 'setosa' oraz 'versicolor'
Iterując po danych rozdziel wiersz na features i label (ostatni)
Zdefiniuj funkcję sum_if(features, label)
Funkcja sumuje features, tylko gdy label jest w select
Gdy label nie występuje w select zwróć 0 (zero)
Wypisz sumę
Porównaj wyniki z sekcją "Output" (patrz poniżej)

Input

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'),
    (7.0, 3.2, 4.7, 1.4, 'versicolor'),
    (7.6, 3.0, 6.6, 2.1, 'virginica'),
    (4.9, 3.0, 1.4, 0.2, 'setosa'),
]

Output

result: float
# 74.9

8.5.4.2. Function Scope Roman to Int¶

Complexity level: medium
Lines of code to write: 15 lines
Estimated time of completion: 15 min
Solution: solution/function_scope_romanint.py

English

Use data from "Input" section (see below)
Define function converting roman numerals to integer

Polish

Użyj danych z sekcji "Input" (patrz poniżej)
Zdefiniuj funkcję przeliczającą liczbę rzymską na całkowitą

Input

CONVERSION = {
    'I': 1,
    'II': 2,
    'III': 3,
    'IV': 4,
    'V': 5,
    'VI': 6,
    'VII': 7,
    'VIII': 8,
    'IX': 9,
    'X': 10,
    'XX': 20,
    'XXX': 30,
    'XL': 40,
    'L': 50,
    'LX': 60,
    'LXX': 70,
    'LXXX': 80,
    'XC': 90,
    'C': 100,
    'D': 500,
    'M': 1000,
}

The whys and wherefores

Defining and calling functions
Checking for corner cases
Passing function arguments
Cleaning data from user input
dict lookups

8.5.4.3. Function Scope Int To Roman¶

Complexity level: medium
Lines of code to write: 15 lines
Estimated time of completion: 15 min
Solution: solution/function_scope_introman.py

English

Use data from "Input" section (see below)
Define function converting integer to roman numerals

Polish

Użyj danych z sekcji "Input" (patrz poniżej)
Zdefiniuj funkcję przeliczającą liczbę całkowitą na rzymską

Input

CONVERSION = {
    'I': 1,
    'II': 2,
    'III': 3,
    'IV': 4,
    'V': 5,
    'VI': 6,
    'VII': 7,
    'VIII': 8,
    'IX': 9,
    'X': 10,
    'XX': 20,
    'XXX': 30,
    'XL': 40,
    'L': 50,
    'LX': 60,
    'LXX': 70,
    'LXXX': 80,
    'XC': 90,
    'C': 100,
    'D': 500,
    'M': 1000,
}

The whys and wherefores

Defining and calling functions
Checking for corner cases
Passing function arguments
Cleaning data from user input
dict lookups