This document provides an overview of key Python concepts including: - Identifiers name variables, types, functions, packages etc. - Data types include numbers, strings, lists, tuples, dictionaries, sets and more. - Control flow statements like if/else and for loops are used without braces. - Functions are defined using the def keyword and can return values. - Modules provide useful functionality like datetime and can be imported. - Python supports OOP with classes, inheritance and methods. - Common libraries are included for tasks like web development, databases and more.

1. Python 3
Claudia Zhou
2014

2. Identifier

3. Names of
• variables
• types
• functions
• packages
• …and so on

4. from Programming in Python 3, Second Edition

5. id(…)
Return the identity of an object.

6. Basics

7. No braces

8. is (not)
• Compare reference
• Use to compare with None

9. Chain comparison
operators
• 0 <= a <= 10
• Evaluating a only once

10. in operator
• Linear search on tuple and list
• Hash on set and dict

11. Boolean
• True, False
• bool()

12. False
• None
• False
• 0, 0.0, 0j - zero of any numeric type
• ‘’, (), [] - any empty sequence
• {} - any empty mapping
• __bool__(), __len__() returns False or 0

13. Logical Operators
• and & or - return operand
• not - returns a Boolean
• x = get_x() or 100

14. Arithmetic Operators
• dividend / produce floating point
• int()
• // produce int
• round(number[, ndigits])

15. Augmented Assignment
• int is immutable - produce new
object
• string - concatenation
• list - extend (append another list)
extend a plain string -> characters

16. Control Flow
Statements

17. else Clause
• if
• while, for
• try

18. Exception
from Programming in Python 3, Second Edition

19. Conditional Expression
• offset = 20
if not sys.platform.startswith(“win"):
offset = 10
• offset = 20 if sys.platform.startswith(“win") else 10
• expression1 if boolean_expression else expression2

20. With Statement
with A() as a, B() as b:
suite
is equivalent to
with A() as a:
with B() as b:
suite

21. Data Types

22. Sequence Types
• list, tuple, range
• str - Text Sequence Type
• bytes, bytearray, memoryview -
Binary Sequance Types

23. Sequence Types
• An iterable which supports efficient
element access using integer indices
via the __getitem__() special method
and defines a __len__() method that
returns the length of the sequence.

24. from Programming in Python 3, Second Edition

25. Slice

26. Slice
a[start:end] # items start through end-1
a[start:] # items start through the rest of the array
a[:end] # items from the beginning through end-1
a[:] # a copy of the whole array
a[start:end:step] # start through not past end, by step

27. Tuple
• Immutable
• a, b = b, a
• a, b, c = get_xxx()
• for x, y in (XXX)

28. Tuple Construction
• empty: ()
• singleton: a, or (a,)
• a, b, c or (a, b, c)
• tuple() or tuple(iterable)

29. Named Tuples
• http://docs.python.org/3/library/
collections.html#namedtuple-factory-
function-for-tuples-with-named-fields

30. List
• Mutable
• find -> sort and binary search

31. List Construction
• empty: []
• [a], [a, b, c]
• list comprehension: [x for x in iterable]
• list() or list(iterable)

32. List Comprehension
• [expression for item in iterable]
• [expression for item in iterable if condifion]
• leaps = [y for y in range(1900, 1940)
if (y % 4 == 0 and y % 100 != 0) or (y% 400
== 0)]

33. Range
• http://docs.python.org/3/library/
stdtypes.html#ranges

34. Set Types
• set - mutable
• frozenset - immutable
• Unordered
• Create: set(), {items} ( {} is dict )

35. Set Comprehension
• {expression for item in iterable}
• {expression for item in iterable if
condition}
• html = {x for x in files if
x.lower().endswith((".htm", ".html"))}

36. Mapping Types
• dict
• Unordered
• http://docs.python.org/3/library/
stdtypes.html#dict

37. Dictionary Comprehension
• {keyexpression: valueexpression for
key, value in iterable}
• {keyexpression: valueexpression for
key, value in iterable if condition}
• file_sizes = {name:
os.path.getsize(name) for name in
os.listdir(“.”) if os.path.isfile(name)}

38. Generator Expression
• (expression for item in iterable)
• (expression for item in iterable if
condition)
• yield - Generator Function

39. defaultdict
• http://docs.python.org/3/library/
collections.html#defaultdict-objects

40. Collection Copying
• Shallow: slice, set.copy(), dict.copy(),
copy.copy()
• Deep: copy.deepcopy()

41. String

42. String Formatting
• http://docs.python.org/3/library/
string.html#string-formatting
"First, thou shalt count to {0}" # References first positional argument
"Bring me a {}" # Implicitly references the first positional argument
"From {} to {}" # Same as "From {0} to {1}"
"My quest is {name}" # References keyword argument 'name'
"Weight in tons {0.weight}" # 'weight' attribute of first positional arg
"Units destroyed: {players[0]}" # First element of keyword argument 'players'.

43. Join Lines
• Escape newline
• Parentheses

44. String Methods
• str.join()
• index & find
• startswith, endswith
• partition
• isdigit() -> unicode
• strip() -> arguments
• http://docs.python.org/3/library/stdtypes.html#string-
methods

45. Path
• Inside Python programs it is
convenient to always use Unix-style
paths,since they can be typed
without the need for escaping, and
they work on all platforms
(includingWindows).

46. Functions

47. Function Definition
• def function_name():
pass

48. Function Characteristics
• def is similar to assignment
• Objects (store in collection, pass as
arguments)
• No overloading

49. 4 Kinds of Functions
• Global
• Local
• Lambda (sort key, defaultdict)
• Method

50. Function Return
• None (default)
• Single value
• A tuple of values

51. Function Parameters
• default value (created at define time)
• positional
• sequence unpacking - *args
• *, no more positional arguments
• keyword

52. Collection Unpacking
• * sequence unpacking operator
• ** mapping unpacking operator

53. Modules & Packages

54. decimal
• http://docs.python.org/3/library/
decimal.html

55. datetime
• http://docs.python.org/3/library/
datetime.html
• class datetime.timedelta
• class dateutil.relativedelta.relativedelta
package: dateutil
module: relativedelta
class: relativedelta

56. IDE & Debugger
• PyCharm - http://www.jetbrains.com/
pycharm/

57. Books

58. Head First Python
Don’t waste time and money

59. Programming in Python 3
Good explanation, bad code

60. Dive Into Python 3
Free

61. Documentation Version

62. Tricks
• python -m http.server 8000

63. Database

64. Python DB API 2.0
• http://www.python.org/dev/peps/
pep-0249/
• Psycopg - PostgreSQL Adapter
http://initd.org/psycopg/

65. import psycopg2
CONNECTION_STRING = 'host=192.168.1.106 dbname=ezfunds
user=ezfunds password=xxxx'

66. with psycopg2.connect(CONNECTION_STRING) as connection:
with connection.cursor() as cursor:
order_type_daily_count = get_order_type_daily_count(
cursor, id_number, order_date, order_type_code, sub_type_code) + 1
cursor.execute(
"""
insert into member_fund_orders(
order_date, id_number, order_type_code, sub_type_code, order_type_daily_count, isin, currency_code,
dividend_option_code, amount, amount_currency_code, order_time, fee_rate, fee_currency_code, fee)
values(%s, %s, %s, %s, %s, %s, %s, %s, %s, %s, %s, %s, %s, %s);
""", (order_date, id_number, order_type_code, sub_type_code, order_type_daily_count, isin,
currency_code, dividend_option_code, amount, amount_currency_code, order_time, fee_rate,
fee_currency_code, fee))
connection.commit()

67. def get_order_type_daily_count(cursor, id_number, order_date, order_type_code, sub_type_code):
"""取得指定條件的最⼤大 order_type_daily_count。
Returns:
⽬目前資料最⼤大的 order_type_daily_count，沒有則回傳 0。
"""
cursor.execute(
"""
select max(order_type_daily_count) from member_fund_orders
where id_number=%s and order_date=%s and order_type_code=%s and sub_type_code=%s;
""", (id_number, order_date, order_type_code, sub_type_code))
return cursor.fetchone()[0] or 0

68. REST API

69. # 3rd
import cherrypy
# Ezfunds
import fund_order
class Subscriptions:
"""包裝單筆下單 REST API 的 class。"""
exposed = True
#@cherrypy.tools.json_out()
#def GET(self, order_date, order_type_code, sub_type_code, id_number, daily_count):
# return {'result': '{} {} {} {} {}'.format(order_date, order_type_code, sub_type_code, id_number,
daily_count)}
@cherrypy.tools.json_in()
def POST(self):
data = cherrypy.request.json
(order_date, sub_type_code, order_type_daily_count) = fund_order.subscribe(**data)
uri = '/orders/subscriptions/{}/{}/{}/{}'.format(
order_date, sub_type_code, data['id_number'], order_type_daily_count)
cherrypy.response.headers['Content-Location'] = uri
return ''

70. def main():
cherrypy.tree.mount(Subscriptions(), '/orders/subscriptions',
{'/': {'request.dispatch': cherrypy.dispatch.MethodDispatcher()}})
cherrypy.tree.mount(Redemptions(), '/orders/redemptions',
{'/': {'request.dispatch': cherrypy.dispatch.MethodDispatcher()}})
cherrypy.tree.mount(Switches(), '/orders/switches',
{'/': {'request.dispatch': cherrypy.dispatch.MethodDispatcher()}})
cherrypy.tree.mount(RedemptionSubscriptions(), '/orders/redemption_subscriptions',
{'/': {'request.dispatch': cherrypy.dispatch.MethodDispatcher()}})
cherrypy.server.bind_addr = ('0.0.0.0', 8080)
cherrypy.engine.start()
cherrypy.engine.block()

72. Chrome
https://chrome.google.com/webstore/detail/advanced-
rest-client/hgmloofddffdnphfgcellkdfbfbjeloo