Study Group: 巾凡哥出品 品質保證 python 02

Access grandparent attributes

• type(suter()) <=class super

• dir(super()) <= no super attribute

• Using OOP design
• Grandparent.attribute / Grandparent.method

Dynamic Programming Language

• Dynamic & Static

  • In computer science, a dynamic programming language is a class of highlevel programming languages, which at runtime execute many common programming behaviours that static programming languages perform during compilation. (Wiki)

    • Static: Java, C#, C, C++, Haskell
    • Dynamic: Python, Javascript, VB, PHP

Dynamic Programming Language

• Definitions of “strong” or “weak”

  • A number of different language design decisions have been referred to as evidence of “strong” or “weak” typing. Many of these are more accurately understood as the presence or absence of type safety, memory safety, static type-checking, or dynamic type-checking.

  • Strong: Java, Python, Haskell, C#, Golang

  • Weak: C, C++, PHP, Javascript, VB

    • C supports more kinds of implicit conversion, and C also allows pointer values to be explicitly cast. For example: void * can be converted to any type of pointer.

Dictionary

grads = { 'Jhon': 20, 'Tom': 40, 'Many': 60}

grades.keys()
grades.values()
grades.get('Jhon') === grades['John']

Tuple

• immutable
• list is mutable

tuple = (1, 2, 3, 4)

a  = ()
print(type(a))
# <class 'typle'>

List Operation

list = [1, 2, 3]
list.append(4) # <= [1, 2, 3, 4]

list = [1, 2, 3]
list.insert(0, 4) # <= [4, 1, 2, 3]


list = [1, 2, 3]
list = [4, 5, 6] + list # <=[4, 5, 6, 1, 2, 3]

list = [1, 2, 3]
list.clear() # <= [ ]

list = [1, 2, 3, 2]
list.remove(2) # <= [1, 3, 2] remove value not index

• index

# vowels list
vowels = ['a', 'e', 'i', 'o', 'i', 'u']

# index of 'e' in vowels
index = vowels.index('e')
print('The index of e:', index)

# element 'i' is searched
# index of the first 'i' is returned
index = vowels.index('i')

print('The index of i:', index)

# alphabets list
alphabets = ['a', 'e', 'i', 'o', 'g', 'l', 'i', 'u']

# index of 'i' in alphabets
index = alphabets.index('e')   # 2
print('The index of e:', index)

# 'i' after the 4th index is searched
index = alphabets.index('i', 4)   # 6
print('The index of i:', index)

# 'i' between 3rd and 5th index is searched
index = alphabets.index('i', 3, 5)   # Error!
print('The index of i:', index)

"""
The index of e: 1
The index of i: 6
Traceback (most recent call last):
  File "*lt;string>", line 13, in 
ValueError: 'i' is not in list
"""

• __getitem__(index):
  • list = [1.0, 2.0, 3.0, 4.0]
  • list.getitem[1] <= return 2.0
  • list.getitem[1] is equivalent to list[1]
  • just use list[index]
• slice

list = ['a', 'b', 'c', 'd', 'e']
list[3:5] # <= ['d', 'e']
list[2:4] # <= ['c', 'd']
list[3:]  # <= ['d', 'e']
list[:2]  # <= ['a', 'b']

list = ['a', 'b', 'c', 'd', 'e']
list[-1]
list[-200]
list[1: -2]
list[ 3: -3]
list[-3, 1]
list[-3:]
以 index start 與 end 最後位置取得 slice

• index & slice

name = 'John'
name[0] # = 'J'
name[-1] # = 'n'
name[-4:] # = 'John'

Converting between datatypes

• tuple to list

data = (1, 2, 3)
list = list(data)

• list to tuple

data = [1, 2, 3]
tuple = tuple(data)

• list to dictionary

data = [["Mary", 20], ["Tom", 10]]
dict123 = dict(data)
print(dict123)
# {'Mary': 20, 'Tom': 10}


dict2 = ((21, 21), (22, 23))
dict2 = dict(dict2)
print(dict2)
# {21: 21, 22: 23}

• print(isinstance(dict, object)) # True