A document for my learning journey in Python - Day 1&2
Reference: https://www.codecademy.com/learn/python
statement: all the following ideas/source codes are the re-creation based on the "codecademy"
1. Indentation is important, e.g.
def spam():
eggs = 12
return eggs
print spam()
//result --> 12
2. Math operation, read more--> https://en.wikibooks.org/wiki/Python_Programming/Basic_Math
a) +
b) -
c) *
d) /
e) ** exponential
d) % modulo, e.g. 3%2 --> 1
3. Escaping character
'This isn\'t flying, this is falling with style!' # To make sure the ( isn't ) is working ( isn\'t )
4. Access by Index
e.g. fifth_letter = "MONTY"[4] #result --> Y
5. String methods
a) len() #e.g. len(test)
b) lower() #e.g. test.lower()
c) upper()
d) str()
#e.g. str(3.14), now 3.14 is string type --> "3.14"
e) string is target --> string equality checking, take note the target cannot have a space in between.
6. String Formatting --> With %
e.g. string_1 = raw_input("What is your name?") #getting the input from user
e.g. string_2 = "place"
e.g. print "Let's not go to %s. 'Tis a silly %s." % (string_1, string_2)
e.g. result --> Let's not go to Camelot. 'Tis a silly place.
7. Date and Time Library
a) Import the library --> from datetime import datetime
b) Datetime methods --> datetime.now() # now.year, now.month, now.day, now.hour, now.minute, now.second
8. Comparators
a) Equal to (==)
b) Not equal to (!=)
c) Less than (<)
d) Less than or equal to (<=)
e) Greater than (>)
f) Greater than or equal to (>=)
9. And (and) and Or (or) operation
**Take note: not is evaluated first, and is evaluated next, or is evaluated last.
a) and --> only two Ture yields True, otherwise False e.g. 00, 01, 10 false, 11 True.
b) or --> only two False yields False, otherwise True e.g. 00 True, 01 10, 11 False.
c) not --> invert
10. Conditional Statement Syntax
a) if ______ : # take note, the semicolon is needed --> :
b) example:
def greater_less_equal_5(answer):
if answer = 5:
return 1
elif answer = "test":
return -1
else:
return 0
11. function
a) keyword --> def test():
e.g. def test ( p1, p2):
e.g. test(1,2)
b) triple quotes --> """ trip;e quotes server the purpose of explaning the funciton""""
12. Generic Import
a) import math --> math.mathmethod() --> allow user to use the methods/functions within the math module
--> import a specific function/method from a module: from math import sqrt
--> import all from a module: from math import * --> this is not so good because it will associate with many unused variables which is not safe
--> get access to all the methods/functions from a module --> everything = dir(math)
13 Analytic method read more: https://community.modeanalytics.com/python/tutorial/python-methods-functions-and-libraries/
a) max()
b) min()
c) abs()
d) type() --> return the type of the varibale within the bracket
-e.g. type(test) == int #checking the type
14. List, using square bracket to indicate it -- name [ ]
a) does not have a fixed length
b) use append to add in parameters --> e.g. list.append(new_item)
c) To access certain parts of the list variables --> list[0:2]
-list[0:2] is using 1st and 2nd items (position 0 and 1) and the list is counting from 0,
-take note, the "2" is larger than the largest number you want to access.
d)List method, list.sort()
e) List association, e.g. list['test1':101, "test2",102]
-This allowed us to access the ID via the 'name'
-This does now allowed us to access the 'name' via the ID
f) List quick method/ dot menthod,
-del list[item1]
g) delete/remove an item
-list.remove[item_name]
15. Dictionary, using curly brackets to indicate it -- name { }
a) Format: d={ 'test':101, "test2":102, ‘key’, 'keyvalue' }
b) Adding element into the Dictionarys -- adding a key to the dictionary, the key can then used to contain List and other types.
-- name ['key'] # adding a new item to the dictionay
-- name ['key'] = keyvalue # keyvalue can be number or string
--e.g. name ['key'] = ['1', '2', '3' ] # adding a list to the key
-- the line at above is able to use to resign the keyvalue to the key
--name[keyvalue] = something #this will reassign the content to the keyvalue
c) How to access an item in the dictionary.
-- e.g. name['key'].sort()
-- e.g. name['key'].remove('item')