位元操作
注意一: 適用範圍 Note that you can only do bitwise operations on an integer. Trying to do them on strings or floats will result in nonsensical output!

print 5 >> 4  # Right Shift
print 5 << 1  # Left Shift
print 8 & 5   # Bitwise AND
print 9 | 4   # Bitwise OR
print 12 ^ 42 # Bitwise XOR
print ~88     # Bitwise NOT
 

print 0b1,    #1
print 0b10,   #2
print 0b11,   #3
print 0b100,  #4
print 0b101,  #5
print 0b110,  #6
print 0b111   #7
print "******"
print 0b1 + 0b11
print 0b11 * 0b11

print bin(1)
for i in range(2,6):
    print bin(i)
 

位元操作 - 將二進位制的str轉換為十進位制的number

print int("1",2)
print int("10",2)
print int("111",2)
print int("0b100",2)
print int(bin(5),2)
# Print out the decimal equivalent of the binary 11001001.
print int("11001001",2)

2 Note that the bitwise | operator can only create results that are greater than or equal to the larger of the two integer inputs.

shift_right = 0b1100
shift_left = 0b1

# Your code here!
shift_right=shift_right >>2
shift_left=shift_left<<2
print bin(shift_right)
print bin(shift_left)

2 just flips all of the bits in a single number

print ~1
print ~2
print ~3
print ~42
print ~123

位元操作-Mask-例1

A bit mask is just a variable that aids you with bitwise operations. A bit mask can help you turn specific bits on, turn others off, or just collect data from an integer about which bits are on or off

判斷右起第4位是否是1，即，判斷右起第4位的開關是否已經開啟

def check_bit4(input):
    input1=int(bin(input),2)
    input2=0b1000
    if(input1&input2):
        return "on"
    else:
        return "off"
        

確保第3為是1

a = 0b10111011
mask=0b100
desired=a|mask
print bin(desired)

a = 0b11101110
mask=0b11111111
desired=a ^ mask
print bin(desired)

def flip_bit(number,n):
    mask=0b1<<(n-1)
    result=mask^number
    return bin(result)

class Fruit(object):
    """A class that makes various tasty fruits."""
    def __init__(self, name, color, flavor, poisonous):
        self.name = name
        self.color = color
        self.flavor = flavor
        self.poisonous = poisonous

    def description(self):
        print "I'm a %s %s and I taste %s." % (self.color, self.name, self.flavor)

    def is_edible(self):
        if not self.poisonous:
            print "Yep! I'm edible."
        else:
            print "Don't eat me! I am super poisonous."

lemon = Fruit("lemon", "yellow", "sour", False)

lemon.description()
lemon.is_edible()

class Animal(object): #object是python中的類，Animal是使用者自定義的類，使用者自定義的類首字母大寫
    def __init__(self,name): #self表示當前的物件，類似C++中的class的*this, 一般放在引數中的第一位。
        self.name=name
        
zebra= Animal("Jeffrey")        
print zebra.name

class ShoppingCart(object):
    """Creates shopping cart objects
    for users of our fine website."""
    items_in_cart = {}
    def __init__(self, customer_name):
        self.customer_name = customer_name

    def add_item(self, product, price):
        """Add product to the cart."""
        if not product in self.items_in_cart:
            self.items_in_cart[product] = price
            print product + " added."
        else:
            print product + " is already in the cart."

    def remove_item(self, product):
        """Remove product from the cart."""
        if product in self.items_in_cart:
            del self.items_in_cart[product]
            print product + " removed."
        else:
            print product + " is not in the cart."

my_cart=ShoppingCart("Goerge")
my_cart.add_item("lemon",3.14)

class Employee(object):
    """Models real-life employees!"""
    def __init__(self, employee_name):
        self.employee_name = employee_name

    def calculate_wage(self, hours):
        self.hours = hours
        return hours * 20.00

# Add your code below! 
class PartTimeEmployee(Employee): #inheritance
    def calculate_wage(self, hours): #override
        self.hours=hours    #because of override, this line have to be here again
        return hours*12.00

class Employee(object):
    """Models real-life employees!"""
    def __init__(self, employee_name):
        self.employee_name = employee_name

    def calculate_wage(self, hours):
        self.hours = hours
        return hours * 20.00

# Add your code below! 
class PartTimeEmployee(Employee): #inheritance
    def calculate_wage(self, hours): #override
        self.hours=hours    #because of override, this line have to be here again
        return hours*12.00
    def full_time_wage(self, hours):
        return super(PartTimeEmployee,self).calculate_wage(hours)

milton = PartTimeEmployee("Milton")
print milton.full_time_wage(10)

class Point3D(object):
    def __init__(self,x,y,z):
        self.x=x
        self.y=y
        self.z=z
    def __repr__(self):
        return "(%d, %d, %d)" % (self.x, self.y, self.z)
    
my_point = Point3D(1,2,3)
print my_point

Python的I/O控制-讀寫檔案操作1

my_list = [i**2 for i in range(1,11)]
# Generates a list of squares of the numbers 1 - 10

f = open("output.txt", "w")

for item in my_list:
    f.write(str(item) + "\n")

f.close()

my_file=open("output.txt","r+")

my_file =open("output.txt","r")
print my_file.read()
my_file.close()

Python的I/O控制-讀寫檔案操作4

my_file=open("text.txt", "r")
print my_file.readline() #readline()每次讀一行
print my_file.readline()
print my_file.readline()
my_file.close()

讀寫檔案操作5 自動關閉檔案

You may not know this, but file objects contain a special pair of built-in methods: __enter__() and __exit__(). The details aren't important, but what is important is that when a file object's __exit__() method is invoked, it automatically closes the file. How do we invoke this method? With with and as.

with open("text.txt", "w") as textfile:
	textfile.write("Success!")

with open("text.txt","w") as my_file:
    my_file.write("hello python")
    
if my_file.closed==False:
    my_file.close()
    
print my_file.closed