分類彙整: python

python built-in function: @classmethod

@classmethod

運用裝飾器語法將一個方法封裝成類方法

class C:

    @classmethod
    def f(cls, arg1, arg2):  # 第一個引述為cls，非self
        pass

class C:

@classmethod

def f(cls, arg1, arg2): # 第一個引述為cls，非self

pass

類方法(classmethod)與靜態方法(static method)差異

類方法可以存取類屬性，也可實例類別對象，可用在工廠模式內加工物件
靜態方法無法訪問類或對象資料，用在輔助特定功能

EX: 類方法與靜態方法

class A:
    @classmethod
    def f1(cls, info):
        print(info)

    @staticmethod
    def f2(info):
        print(info)


class B(A):
    pass


A.f1('test')     # test
A.f2('test')     # test
B.f1('B test')   # B test

class A:

@classmethod

def f1(cls, info):

print(info)

@staticmethod

def f2(info):

print(info)

class B(A):

pass

A.f1('test') # test

A.f2('test') # test

B.f1('B test') # B test

EX: 一般方法與類方法存取類屬性

class B:

    data = 1

    @classmethod
    def f1(cls):
        print("class method")
        print(cls.data)

    def f3(self):
        self.data += 10


B.f1()         # 1

b = B()
b.f3()
print(a.data)  # 11

B.f1()         # 1，類方法存取類屬性不會被其他類物件修改

class B:

data = 1

@classmethod

def f1(cls):

print("class method")

print(cls.data)

def f3(self):

self.data += 10

B.f1() # 1

b = B()

b.f3()

print(a.data) # 11

B.f1() # 1，類方法存取類屬性不會被其他類物件修改

python built-in function: callable

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callable(object, /)

判斷object是否可呼叫，若可呼叫則回傳True
函數與類別可呼叫，若類別實作__call__函數，其實例也可以呼叫

EX: 比較函數與基本類型是否可呼叫

def f():
    return 5

print(callable(f))    # True

x = 5
print(callable(x))    # False，int不可呼叫

y = "123"
print(callable(y))    # False，str不可呼叫

def f():

return 5

print(callable(f)) # True

x = 5

print(callable(x)) # False，int不可呼叫

y = "123"

print(callable(y)) # False，str不可呼叫

EX: 類別與其實例是否可呼叫

class A:
    def __init__(self):
        pass

a = A()
print(callable(A))            # True
print(callable(a))            # False，未實現__call__，實例不可呼叫


class B:
    def __call__(self):
        print('This is B')

b = B()
print(callable(b))            # True

class A:

def __init__(self):

pass

a = A()

print(callable(A)) # True

print(callable(a)) # False，未實現__call__，實例不可呼叫

class B:

def __call__(self):

print('This is B')

b = B()

print(callable(b)) # True

python built-in function: chr

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chr(i, /)

回傳該字元的Unicode編碼位置為整數i的字串
其中i範圍限制: 0 ~ 1,114,111(0x10FFFF)

PS: ord() 與 chr() 互相轉換

# -*- coding: utf-8 -*-

# unicode編碼位置轉換成字元
for i in [65, 90, 97, 122]:
    print("%s: %s" % (i, chr(i)))
# 65: A
# 90: Z
# 97: a
# 122: z

# 字元轉換成unicode編碼位置
print(ord('a'))   # 97

# -*- coding: utf-8 -*-

# unicode編碼位置轉換成字元

for i in [65, 90, 97, 122]:

print("%s: %s" % (i, chr(i)))

# 65: A

# 90: Z

# 97: a

# 122: z

# 字元轉換成unicode編碼位置

print(ord('a')) # 97

python built-in function: bin

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bin(x, /)

將一個整數轉變為一個前綴為 “0b” 的二進位製字串

# -*- coding: utf-8 -*-

print(bin(3))     # 0b11
print(bin(-10))   # -0b1010

# 將二進為字串轉換回int
print(int(bin(3), 2))    # 3
print(int(bin(-10), 2))  # -10

# 移除"0b"前綴
print(format(14, '#b'), format(14, 'b'))   # ('0b1110', '1110')
print(f'{14:#b}', f'{14:b}')               # ('0b1110', '1110')


print(format(14, '#b'), format(14, 'b'))   # ('0b1110', '1110')

print(f'{14:#b}', f'{14:b}')               # ('0b1110', '1110')

# -*- coding: utf-8 -*-

print(bin(3)) # 0b11

print(bin(-10)) # -0b1010

# 將二進為字串轉換回int

print(int(bin(3), 2)) # 3

print(int(bin(-10), 2)) # -10

# 移除"0b"前綴

print(format(14, '#b'), format(14, 'b')) # ('0b1110', '1110')

print(f'{14:#b}', f'{14:b}') # ('0b1110', '1110')

print(format(14, '#b'), format(14, 'b')) # ('0b1110', '1110')

print(f'{14:#b}', f'{14:b}') # ('0b1110', '1110')

python build-in function: ascii

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ascii(object, /)

與repr()相似，回傳一個表示物件的字串，但repr()中非ASCII編碼的字元會被跳脫

\x: 十六進制
\u, \U: unicode碼

# -*- coding: utf-8 -*-

ch_str = "測試"
s = ascii(ch_str)    # '\u6e2c\u8a66'

# 將ascii轉回字串
print(s.encode('ascii').decode('unicode_escape'))      # 測試
# or
print(s.encode().decode('unicode_escape'))             # 測試

# -*- coding: utf-8 -*-

ch_str = "測試"

s = ascii(ch_str) # '\u6e2c\u8a66'

# 將ascii轉回字串

print(s.encode('ascii').decode('unicode_escape')) # 測試

# or

print(s.encode().decode('unicode_escape')) # 測試

python built-in function: any

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any(iterable, /)

如果 iterable 的任一元素為真，回傳 True。如果 iterable 是空的，則回傳 False

print(any(['a', 'b', 'c', 'd']))    # True
print(any(['a', 'b', '', 'd']))     # True
print(any([0, False, '']))          # False
print(any([0, 0, 0, 0]))            # False
print(any([0, 0, 1, 0]))            # True
print(any([]))                      # False

print(any(['a', 'b', 'c', 'd'])) # True

print(any(['a', 'b', '', 'd'])) # True

print(any([0, False, ''])) # False

print(any([0, 0, 0, 0])) # False

print(any([0, 0, 1, 0])) # True

print(any([])) # False

PS:
all: iterable 內所有元素皆為True則回傳 True，若iterable 為空則回傳True

python built-in function: all

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all(iterable, /)

當iterable內所有元素為True時或iterable為空，則回傳True

print(all(['a', 'b', 'c', 'd']))    # True
print(all(['a', 'b', '', 'd']))     # False
print(all([0, 1, 1, 1]))            # False
print(all([]))                      # True

print(all(['a', 'b', 'c', 'd'])) # True

print(all(['a', 'b', '', 'd'])) # False

print(all([0, 1, 1, 1])) # False

print(all([])) # True

PS:
any: 任一元素為True時回傳True，iterable為空則回傳False

python built-in function: zip

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zip(*iterables, strict=False)

*iterables:
可迭代物件

strict:
當設定為True，若可迭代物件長度不一致時，會產生異常

x = ['a', 'b', 'c']
y = [1, 2, 3]
print(list(zip(x, y)))
# [('a', 1), ('b', 2), ('c', 3)]

z = [4, 5, 6, 7]
print(list(zip(x, z, strict=True)))
# ValueError: zip() argument 2 is longer than argument 1

x = ['a', 'b', 'c']

y = [1, 2, 3]

print(list(zip(x, y)))

# [('a', 1), ('b', 2), ('c', 3)]

z = [4, 5, 6, 7]

print(list(zip(x, z, strict=True)))

# ValueError: zip() argument 2 is longer than argument 1

使用zip搭配for loop，可非常簡潔地產生座標給PyQt QGridLayout使用
positions list中的元素為 tuple，zip產生的position也是tuple

拆解:
positions list: [(0, 0), (0, 1), …, (4, 3)]
list(zip(positions, name)): [((0, 0), ‘Cls’), ((0, 1), ‘Black’), …, ((4, 3), ‘+’)]
position: (0, 0), …, (4, 3)
name: Cls, Back, …, +

# -*- coding: utf-8 -*-
import sys
from PyQt5.QtWidgets import QApplication, QWidget, QGridLayout, QPushButton


class Winform(QWidget):
    def __init__(self, parent=None):
        super(Winform, self).__init__(parent)
        self.initUI()

    def initUI(self):
        grid = QGridLayout()
        self.setLayout(grid)

        names = ['Cls', 'Back', '', 'Close',
                 '7', '8', '9', '/',
                 '4', '5', '6', '*',
                 '1', '2', '3', '-',
                 '0', '.', '=', '+']

        positions = [(i, j) for i in range(5) for j in range(4)]
        for position, name in zip(positions, names):
            if name == '':
                continue

            button = QPushButton(name)
            # addWidget(QWidget widget, int row, int col, int alignment=0)
            # position: (0, 0) ~ (4, 3)
            # *position: 0 0 ~ 4 3
            grid.addWidget(button, *position)

        self.move(300, 150)
        self.setWindowTitle('網格佈局')


if __name__ == "__main__":
    app = QApplication(sys.argv)
    form = Winform()
    form.show()
    sys.exit(app.exec_())

# -*- coding: utf-8 -*-

import sys

from PyQt5.QtWidgets import QApplication, QWidget, QGridLayout, QPushButton

class Winform(QWidget):

def __init__(self, parent=None):

super(Winform, self).__init__(parent)

self.initUI()

def initUI(self):

grid = QGridLayout()

self.setLayout(grid)

names = ['Cls', 'Back', '', 'Close',

'7', '8', '9', '/',

'4', '5', '6', '*',

'1', '2', '3', '-',

'0', '.', '=', '+']

positions = [(i, j) for i in range(5) for j in range(4)]

for position, name in zip(positions, names):

if name == '':

continue

button = QPushButton(name)

# addWidget(QWidget widget, int row, int col, int alignment=0)

# position: (0, 0) ~ (4, 3)

# *position: 0 0 ~ 4 3

grid.addWidget(button, *position)

self.move(300, 150)

self.setWindowTitle('網格佈局')

if __name__ == "__main__":

app = QApplication(sys.argv)

form = Winform()

form.show()

sys.exit(app.exec_())

python built-in function: map

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map(function, iterable, *iterables)
返回結果是一個列表，不改變原有的list，而是返回一個新的list

function:
回傳的是一個函數名，可以是python內置的，也可以是自定義

iterable:
回傳的是一個可以迭代的對象，例如列表、元組、字符串

a = (1, 2, 3, 4, 5)
b = [1, 2, 3, 4, 5]
c = "abcdef"

print(map(str, a))        # <map object at 0x00000281B591B0B8>    返回一個map對象
print(list(map(str, a)))  # ['1', '2', '3', '4', '5']             將map對象列表顯示出來

print(map(str, b))        # <map object at 0x00000230BB7F3358>
print(list(map(str, b)))  # ['1', '2', '3', '4', '5']

print(map(str, c))        # <map object at 0x00000230BB7FB0B8>
print(list(map(str, c)))  # ['a', 'b', 'c', 'd', 'e', 'f']

a = (1, 2, 3, 4, 5)

b = [1, 2, 3, 4, 5]

c = "abcdef"

print(map(str, a)) # <map object at 0x00000281B591B0B8> 返回一個map對象

print(list(map(str, a))) # ['1', '2', '3', '4', '5'] 將map對象列表顯示出來

print(map(str, b)) # <map object at 0x00000230BB7F3358>

print(list(map(str, b))) # ['1', '2', '3', '4', '5']

print(map(str, c)) # <map object at 0x00000230BB7FB0B8>

print(list(map(str, c))) # ['a', 'b', 'c', 'd', 'e', 'f']

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分類彙整: python

python built-in function: @classmethod

python built-in function: callable

python built-in function: chr

python built-in function: bin

python build-in function: ascii

python built-in function: any

python built-in function: all

python built-in function: zip

python built-in function: map