![A little about me
{
“Name”: “Pedro Rodrigues”,
“Origin”: {“Country”: “Angola”, “City”: “Luanda”},
“Lives”: [“Netherlands”, 2013],
“Past”: [“CTO”, “Senior Backend Engineer”],
“Present”: [“Freelance Software Engineer”, “Coach”],
“Other”: [“Book author”, “Start a Career with Python”]
}](https://image.slidesharecdn.com/introductionpart3-161125224917/85/Introduction-to-the-basics-of-Python-programming-part-3-2-320.jpg)
![A little recap
>>> x = [1, 2]
>>> x
[1, 2]
>>> x = {1, 2}
>>> x
{1, 2}
>>> x = {"one": 1, "two": 2}
>>> x
{'two': 2, 'one': 1}](https://image.slidesharecdn.com/introductionpart3-161125224917/85/Introduction-to-the-basics-of-Python-programming-part-3-9-320.jpg)
![A little recap
colors = ["red", "green", "blue", "yellow", "purple"]
for color in colors:
if len(color) > 4:
print(color)
stack = [1, 2, 3]
while len(stack) > 0:
print(stack.pop())](https://image.slidesharecdn.com/introductionpart3-161125224917/85/Introduction-to-the-basics-of-Python-programming-part-3-12-320.jpg)
![A little recap
>>> colors = ["red", "green", "blue", "yellow", "purple"]
>>> colors_iter = colors.__iter__()
>>> colors_iter
<list_iterator object at 0x100c7a160>
>>> colors_iter.__next__()
'red'
…
>>> colors_iter.__next__()
'purple'
>>> colors_iter.__next__()
Traceback (most recent call last): File "<stdin>", line 1, in
<module>
StopIteration](https://image.slidesharecdn.com/introductionpart3-161125224917/85/Introduction-to-the-basics-of-Python-programming-part-3-14-320.jpg)
![A little recap
colors = [(0, "red"), (1, "blue"), (2, "green"), (3, "yellow")]
for index, color in colors:
print(index, " --> ", color)
colors = ["red", "blue", "green", "yellow", "purple"]
for index, color in enumerate(colors):
print(index, " --> ", color)](https://image.slidesharecdn.com/introductionpart3-161125224917/85/Introduction-to-the-basics-of-Python-programming-part-3-15-320.jpg)
![A little recap
colors = ["red", "green", "blue", "yellow", "purple"]
new_colors = []
for color in colors:
if len(color) > 4:
new_colors.append(color)
new_colors = [color for color in colors if len(color) > 4]](https://image.slidesharecdn.com/introductionpart3-161125224917/85/Introduction-to-the-basics-of-Python-programming-part-3-17-320.jpg)
![Challenge
Given a list of colors, create a new list with all the colors in uppercase. Use list
comprehensions.
colors = ["red", "green", "blue", "yellow", "purple"]
upper_colors = []
for color in colors:
upper_colors.append(color.upper())](https://image.slidesharecdn.com/introductionpart3-161125224917/85/Introduction-to-the-basics-of-Python-programming-part-3-18-320.jpg)
![A little recap
squares = {}
for i in range(10):
squares[i] = i**2
squares = {i:i**2 for i in range(10)}
{0: 0, 1: 1, 2: 4, 3: 9, 4: 16, 5: 25, 6: 36, 7: 49, 8: 64, 9:
81}](https://image.slidesharecdn.com/introductionpart3-161125224917/85/Introduction-to-the-basics-of-Python-programming-part-3-20-320.jpg)
![Challenge
Given a list of colors, create a dictionary where each key is a color and the value is
the color written backwards. Use dict comprehensions.
colors = ["red", "green", "blue", "yellow", "purple"]
backwards_colors = {}
for color in colors:
backwards_colors[color] = color[::-1]](https://image.slidesharecdn.com/introductionpart3-161125224917/85/Introduction-to-the-basics-of-Python-programming-part-3-21-320.jpg)
![A little recap
def add_aquares(*args):
if len(args) == 2:
return args[0]**2 + args[1]**2
>>> add_squares(2, 3)
13](https://image.slidesharecdn.com/introductionpart3-161125224917/85/Introduction-to-the-basics-of-Python-programming-part-3-25-320.jpg)
![A little recap
def add_squares(**kwargs):
if len(kwargs) == 2:
return kwargs["a"]**2 + kwargs["b"]**2
>>> add_squares(a=2, b=3)
13](https://image.slidesharecdn.com/introductionpart3-161125224917/85/Introduction-to-the-basics-of-Python-programming-part-3-26-320.jpg)
![Challenge
Define a function that turns a string into a list of int (operands) and strings (operators) and returns
the list.
>>> _convert_expression("4 3 +")
[4, 3, "+"]
>>> _convert_expression("4 3 + 2 *")
[4, 3, "+", 2, "*"]
Hints:
“a b”.split(“ “) = [“a”, “b”]
“a”.isnumeric() = False
int(“2”) = 2
Kudos for who solves in one line using lambdas and list comprehensions.](https://image.slidesharecdn.com/introductionpart3-161125224917/85/Introduction-to-the-basics-of-Python-programming-part-3-27-320.jpg)
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Introduction to the basics of Python programming (part 3)
- 1. Introduction to the basics of Python programming (PART 3) by Pedro Rodrigues ([email protected])
- 2. A little about me { “Name”: “Pedro Rodrigues”, “Origin”: {“Country”: “Angola”, “City”: “Luanda”}, “Lives”: [“Netherlands”, 2013], “Past”: [“CTO”, “Senior Backend Engineer”], “Present”: [“Freelance Software Engineer”, “Coach”], “Other”: [“Book author”, “Start a Career with Python”] }
- 3. Why this Meetup Group? Promote the usage of Python Gather people from different industries and backgrounds Teach and Learn
- 4. What will be covered Recap of Parts 1 and 2 import, Modules and Packages Python in action Note: get the code here: https://dl.dropboxusercontent.com/u/10346356/session3.zip
- 5. A little recap Python is an interpreted language (CPython is the reference interpreter) Variables are names bound to objects stored in memory Data Types: immutable or mutable Data Types: Numbers (int, float, bool), Sequences (str, tuple, list, bytes, bytearray), set, dict Control Flow: if statement, for loop, while loop Iterables are container objects capable of returning their elements one at a time Iterators implement the methods __iter__ and __next__
- 6. A little recap Python is an interpreted language (CPython is the reference interpreter) Variables are names bound to objects stored in memory Data Types: immutable or mutable Data Types: Numbers (int, float, bool), Sequences (str, tuple, list, bytes, bytearray), set, dict Control Flow: if statement, for loop, while loop Iterables are container objects capable of returning their elements one at a time Iterators implement the methods __iter__ and __next__
- 7. A little recap Python is an interpreted language (CPython is the reference interpreter) Variables are names bound to objects stored in memory Data Types: immutable or mutable Data Types: Numbers (int, float, bool), Sequences (str, tuple, list, bytes, bytearray), set, dict Control Flow: if statement, for loop, while loop Iterables are container objects capable of returning their elements one at a time Iterators implement the methods __iter__ and __next__
- 8. A little recap >>> 2 + 2 4 >>> 4 / 2 2.0 >>> 4 > 2 True >>> x = 1, 2 >>> x (1, 2)
- 9. A little recap >>> x = [1, 2] >>> x [1, 2] >>> x = {1, 2} >>> x {1, 2} >>> x = {"one": 1, "two": 2} >>> x {'two': 2, 'one': 1}
- 10. A little recap Python is an interpreted language (CPython is the reference interpreter) Variables are names bound to objects stored in memory Data Types: immutable or mutable Data Types: Numbers (int, float, bool), Sequences (str, tuple, list, bytes, bytearray), set, dict Control Flow: if statement, for loop, while loop Iterables are container objects capable of returning their elements one at a time Iterators implement the methods __iter__ and __next__
- 11. A little recap if x % 3 == 0 and x % 5 == 0: return "FizzBuzz" elif x % 3 == 0: return "Fizz" elif x % 5 == 0: return "Buzz" else: return x
- 12. A little recap colors = ["red", "green", "blue", "yellow", "purple"] for color in colors: if len(color) > 4: print(color) stack = [1, 2, 3] while len(stack) > 0: print(stack.pop())
- 13. A little recap Python is an interpreted language (CPython is the reference interpreter) Variables are names bound to objects stored in memory Data Types: immutable or mutable Data Types: Numbers (int, float, bool), Sequences (str, tuple, list, bytes, bytearray), set, dict Control Flow: if statement, for loop, while loop Iterables are container objects capable of returning their elements one at a time Iterators implement the methods __iter__ and __next__
- 14. A little recap >>> colors = ["red", "green", "blue", "yellow", "purple"] >>> colors_iter = colors.__iter__() >>> colors_iter <list_iterator object at 0x100c7a160> >>> colors_iter.__next__() 'red' … >>> colors_iter.__next__() 'purple' >>> colors_iter.__next__() Traceback (most recent call last): File "<stdin>", line 1, in <module> StopIteration
- 15. A little recap colors = [(0, "red"), (1, "blue"), (2, "green"), (3, "yellow")] for index, color in colors: print(index, " --> ", color) colors = ["red", "blue", "green", "yellow", "purple"] for index, color in enumerate(colors): print(index, " --> ", color)
- 16. A little recap List comprehensions Dictionary comprehensions Functions Positional Arguments Keyword Arguments Default parameters Variable number of arguments
- 17. A little recap colors = ["red", "green", "blue", "yellow", "purple"] new_colors = [] for color in colors: if len(color) > 4: new_colors.append(color) new_colors = [color for color in colors if len(color) > 4]
- 18. Challenge Given a list of colors, create a new list with all the colors in uppercase. Use list comprehensions. colors = ["red", "green", "blue", "yellow", "purple"] upper_colors = [] for color in colors: upper_colors.append(color.upper())
- 19. A little recap List comprehensions Dictionary comprehensions Functions Positional Arguments Keyword Arguments Default parameters Variable number of arguments
- 20. A little recap squares = {} for i in range(10): squares[i] = i**2 squares = {i:i**2 for i in range(10)} {0: 0, 1: 1, 2: 4, 3: 9, 4: 16, 5: 25, 6: 36, 7: 49, 8: 64, 9: 81}
- 21. Challenge Given a list of colors, create a dictionary where each key is a color and the value is the color written backwards. Use dict comprehensions. colors = ["red", "green", "blue", "yellow", "purple"] backwards_colors = {} for color in colors: backwards_colors[color] = color[::-1]
- 22. A little recap List comprehensions Dictionary comprehensions Functions Positional Arguments Keyword Arguments Default parameters Variable number of arguments
- 23. A little recap def say_hello(): print("Hello") def add_squares(a, b): return a**2 + b**2 >>> add_squares(2, 3) 13 def add_squares(a, b=3): return a**2 + b**2 >>> add_squares(2) 13
- 24. A little recap def add_squares(a, b): return a**2 + b**2 >>> add_squares(b=3, a=2) 13
- 25. A little recap def add_aquares(*args): if len(args) == 2: return args[0]**2 + args[1]**2 >>> add_squares(2, 3) 13
- 26. A little recap def add_squares(**kwargs): if len(kwargs) == 2: return kwargs["a"]**2 + kwargs["b"]**2 >>> add_squares(a=2, b=3) 13
- 27. Challenge Define a function that turns a string into a list of int (operands) and strings (operators) and returns the list. >>> _convert_expression("4 3 +") [4, 3, "+"] >>> _convert_expression("4 3 + 2 *") [4, 3, "+", 2, "*"] Hints: “a b”.split(“ “) = [“a”, “b”] “a”.isnumeric() = False int(“2”) = 2 Kudos for who solves in one line using lambdas and list comprehensions.
- 28. Challenge RPN = Reverse Polish Notation 4 3 + (7) 4 3 + 2 * (14) Extend RPN calculator to support the operators *, / and sqrt (from math module). import math print(math.sqrt(4))
- 29. Modules and Packages A module is a file with definitions and statements It’s named after the file. Modules are imported with import statement import <module> from <module> import <name1> from <module> import <name1>, <name2> import <module> as <new_module_name> from <module> import <name1> as <new_name1> from <module> import *
- 30. Modules and Packages A package is a directory with a special file __init__.py (the file can be empty, and it’s also not mandatory to exist) The file __init__.py is executed when importing a package. Packages can contain other packages.
- 31. Modules and Packages api/ __init__.py rest.py server.py services/ __init__.py rpn.py hello.py $ python -m api.server
- 32. Modules and Packages import api from api import rest import api.services.rpn from api.services.hello import say_hello
- 33. Challenge Extend functionalities of the RESTful API: Add a handler for http://localhost:8080/calculate This handler should accept only the POST method. Put all the pieces together in the rpn module.
- 34. Reading material List comprehensions: https://docs.python.org/3.5/tutorial/datastructures.html#list- comprehensions Dict comprehensions: https://docs.python.org/3.5/tutorial/datastructures.html#dictionaries Functions and parameters: https://docs.python.org/3.5/reference/compound_stmts.html#function-definitions Names, Namespaces and Scopes: https://docs.python.org/3.5/tutorial/classes.html#a-word-about-names-and- objects
- 35. More resources Python Tutorial: https://docs.python.org/3/tutorial/index.html Python Language Reference: https://docs.python.org/3/reference/index.html Slack channel: https://startcareerpython.slack.com/ Start a Career with Python newsletter: https://www.startacareerwithpython.com/ Book: Start a Career with Python Book 15% off (NZ6SZFBL): https://www.createspace.com/6506874
Editor's Notes
- #20: Similar to list comprehensions