programowanie:python:start [wiki.sases.pl]

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====== Python ======
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===== Środowisko wirtualne =====
  * Utworzenie i uruchomienie
<code>
python -m venv env
source env/bin/activate
</code>

  * Opuszczenie
<code>
deactivate
</code>
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===== Try =====
<code python>
try:
  print("Hello")
except NamedError:  // obsługa konkretnego błędu
  print("NamedError occurred")
except:  // obsługa jakiegokolwiek błędu
  print("Something went wrong")
except Exception as e: // obsługa jakiegokolwiek błędu z informacją zwrotną co to za błąd
  print("The error is: ",e)
else:  // jeżeli nie wystąpił żaden błąd
  print("Nothing went wrong")
finally:  // po obsłużeniu wszystkiego powyższego
  print("The 'try except' is finished")


if ...:  
  raise TypeError("My Error occurred")
</code>
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=== Built-in Exceptions ===
^ Exception ^ Description ^
| ArithmeticError | Raised when an error occurs in numeric calculations |
| AssertionError | Raised when an assert statement fails |
| AttributeError | Raised when attribute reference or assignment fails |
| Exception | Base class for all exceptions |
| EOFError | Raised when the input() method hits an "end of file" condition (EOF) |
| FloatingPointError | Raised when a floating point calculation fails |
| GeneratorExit | Raised when a generator is closed (with the close() method) |
| ImportError | Raised when an imported module does not exist |
| IndentationError | Raised when indentation is not correct |
| IndexError | Raised when an index of a sequence does not exist |
| KeyError | Raised when a key does not exist in a dictionary |
| KeyboardInterrupt | Raised when the user presses Ctrl+c, Ctrl+z or Delete |
| LookupError | Raised when errors raised cant be found |
| MemoryError | Raised when a program runs out of memory |
| NameError | Raised when a variable does not exist |
| NotImplementedError | Raised when an abstract method requires an inherited class to override the method |
| OSError | Raised when a system related operation causes an error |
| OverflowError | Raised when the result of a numeric calculation is too large |
| ReferenceError | Raised when a weak reference object does not exist |
| RuntimeError | Raised when an error occurs that do not belong to any specific exceptions |
| StopIteration | Raised when the next() method of an iterator has no further values |
| SyntaxError | Raised when a syntax error occurs |
| TabError | Raised when indentation consists of tabs or spaces |
| SystemError | Raised when a system error occurs |
| SystemExit | Raised when the sys.exit() function is called |
| TypeError | Raised when two different types are combined |
| UnboundLocalError | Raised when a local variable is referenced before assignment |
| UnicodeError | Raised when a unicode problem occurs |
| UnicodeEncodeError | Raised when a unicode encoding problem occurs |
| UnicodeDecodeError | Raised when a unicode decoding problem occurs |
| UnicodeTranslateError | Raised when a unicode translation problem occurs |
| ValueError | Raised when there is a wrong value in a specified data type |
| ZeroDivisionError | Raised when the second operator in a division is zero |
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===== MySQL =====

Instalacja biblioteki: ''pip install mysql-connector-python''\\
Oficjalna dokumentacja: [[https://dev.mysql.com/doc/connector-python/en/connector-python-example-connecting.html]]\\

Przykład:
<code python>

DB_CONFIG = {
  'user': 'scott',
  'password': 'password',
  'host': '127.0.0.1',
  'database': 'employees',
  'raise_on_warnings': True
}

db = mysql.connector.connect(**DB_CONFIG)
cursor = db.cursor(buffered=True)

cursor.execute(f"SELECT * FROM ...;")
result = cursor.fetchall()
result = cursor.fetchone()
cursor.close()

sql = "INSERT INTO books (url, isbn) VALUES (%s, %s)"
val = ('url_val', 'isbn_val')
cursor.execute(sql, val)
db.commit()
added_id = cursor.lastrowid

db.close()
</code>
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===== Obiektowo =====
W Python nie ma czegoś takiego jak prywatne/publiczne. Stosowane są podkreślniki przed nazwą aby wskazać, że to jest używane jak prywatne.

<code python>
class ZeissReport:

    def __init__(self, file):
        self._file = file  // właściwość podawana przy inicjalizacji
        self._part = None  // właściwość z wartością ustawianą później
        self._results = []

        self._readPdf()  // funkcja wywołana w trakcie inicjalizacji

    @property
    def part(self):  // odczyt właściwości - Getter
        return self._part
    
    @property
    def results(self):
        return self._results
        
    @part.setter  // ustawienie właściwości - Setter
    def part(self, value):
        if value < 1:
            raise ValueError("Part below 1 is not possible")
        self._part = value
            
    def _readPdf(self):  // funkcja
       ...
       
       self._part = ...
       self._results = ...
</code>