Python

Crear

  python3 -m venv /path/to/new/virtual/environment
  python -m pip install --user --upgrade pip

Usar

  source <venv>/bin/activate
  deactivate

Instalar paquete

  # Download and unzip
  pip install requests
  pip install -r requirements.txt

Freezing dependencies

  pip freeze # To create requirements.txt

• List is a collection which is ordered and changeable. Allows duplicate members.
• Tuple is a collection which is ordered and unchangeable. Allows duplicate members.
• Set is a collection which is unordered, unchangeable, and unindexed. No duplicate members.
• Dictionary is a collection which is ordered and changeable. No duplicate members.

  x = ["apple", "banana", "cherry"]   # list
  x = ("apple", "banana", "cherry")   # tuple
  x = range(6)                        # range
  x = {"name" : "John", "age" : 36}   # dict
  x = {"apple", "banana", "cherry"}   # set
  x = frozenset({"apple", "banana", "cherry"})  # frozenset

  x = str("Hello World")      str
  x = int(20) int
  x = float(20.5)     float
  x = complex(1j)     complex
  x = list(("apple", "banana", "cherry"))     list
  x = tuple(("apple", "banana", "cherry"))    tuple
  x = range(6)        range
  x = dict(name="John", age=36)       dict
  x = set(("apple", "banana", "cherry"))      set
  x = frozenset(("apple", "banana", "cherry"))        frozenset
  x = bool(5) bool
  x = bytes(5)        bytes
  x = bytearray(5)    bytearray
  x = memoryview(bytes(5)) memoryview

  a = "Hello, World!"
  print(a[1])
  for x in "banana":
      print(x)
  b = "Hello, World!"
  print(b[2:5])
  print(b[:5])
  print(b[2:])
  print(b[-5:-2])

  txt = "The best things in life are free!"
  print("free" in txt)
  txt = "The best things in life are free!"
  if "free" in txt:
      print("Yes, 'free' is present.")

  age = 36
  txt = "My name is John, and I am {}"
  print(txt.format(age))
  
  quantity = 3
  itemno = 567
  price = 49.95
  myorder = "I want to pay {2} dollars for {0} pieces of item {1}."
  print(myorder.format(quantity, itemno, price))
  
  return f"{self.name}({self.age})"
  
  print(f"asdfdfsas {}")

  class Person:
      def __init__(self, fname, lname, age):
          self.firstname = fname
          self.lastname = lname
          self.age = age
      def __str__(self):
          return f"{self.firstname}({self.age})"
      def printname(self):
          print(self.firstname, self.lastname)
  p1 = Person("John", "Smith", 36)
  print(p1)
  p1.printname()
  del p1
  
  class Student(Person): # Herencia
      def __init__(self, fname, lname, age):
          super().__init__(self, fname, lname, age)
          self.graduationyear = 2019

  try:
      print(x)
  except NameError:
      print("Variable x is not defined")
  except:
      print("An exception occurred")
  else:
      print("Nothing went wrong")
  
  raise Exception("Sorry, no numbers below zero")
  raise TypeError("Only integers are allowed")

This module provides a decorator and functions for automatically adding generated special methods such as \_\_init\_\_(), eq() and \_\_repr\_\_() to user-defined classes.

  from dataclasses import dataclass
  @dataclass
  class InventoryItem:
      """Class for keeping track of an item in inventory."""
      name: str
      unit_price: float
      quantity_on_hand: int = 0
      x: int
      y: int = field(repr=False)
      z: int = field(repr=False, default=10)
      t: int = 20
      mylist: list = field(default_factory=list)
  
      def total_cost(self) -> float:
          return self.unit_price * self.quantity_on_hand

import sqlite3   
try:
    sqlite_Connection = sqlite3.connect('temp.db')
    conn = sqlite3.connect(':memory:')
    print("\nMemory database created and connected to SQLite.")
    sqlite_select_Query = "select sqlite_version();"
    conn.execute(sqlite_select_Query)
    print("\nSQLite Database Version is: ", sqlite3.version)
    conn.close()
except sqlite3.Error as error:
    print("\nError while connecting to sqlite", error)
finally:
    if (sqlite_Connection):
        sqlite_Connection.close()
        print("\nThe SQLite connection is closed.")

  import sqlite3
  from sqlite3 import Error
  
  def sql_connection():
      try:
          conn = sqlite3.connect('mydatabase.db')
          return conn
      except Error:
          print(Error)
  
  def sql_table(conn):
      cursorObj = conn.cursor()
      # Create the table
      cursorObj.execute("""
          CREATE TABLE salesman(salesman_id n(5), 
                                  name char(30), 
                                  city char(35), 
                                  commission decimal(7,2));
      """)
      # Insert records
      cursorObj.executescript("""
      INSERT INTO salesman VALUES(5001,'James Hoog', 'New York', 0.15);
      INSERT INTO salesman VALUES(5002,'Nail Knite', 'Paris', 0.25);
      INSERT INTO salesman VALUES(5003,'Pit Alex', 'London', 0.15);
      INSERT INTO salesman VALUES(5004,'Mc Lyon', 'Paris', 0.35);
      INSERT INTO salesman VALUES(5005,'Paul Adam', 'Rome', 0.45);
      """)
      conn.commit()
      cursorObj.execute("SELECT * FROM salesman")
      rows = cursorObj.fetchall()
      print("Agent details:")
      for row in rows:
          print(row)
          print("\nUpdate all commision to .55:")
      sql_update_query = """Update salesman set commission = .55"""
      cursorObj.execute(sql_update_query)
      conn.commit()
      print("Record Updated successfully ")
      cursorObj.execute("SELECT * FROM salesman")
      rows = cursorObj.fetchall()
      print("\nAfter updating Agent details:")
      for row in rows:
          print(row)
  sqllite_conn = sql_connection()
  sql_table(sqllite_conn)
  if (sqllite_conn):
      sqllite_conn.close()
      print("\nThe SQLite connection is closed.")

exc\_info = sys.exc\_info() print(’’.join(traceback.format\_exception(\*exc\_info)))