python 快速入門(三)
阿新 • • 發佈:2018-12-09
九. 類
1.建立類
class Dog():
"""一次模擬小狗的簡單嘗試"""
def __init__(self, name, age):
"""初始化屬性name和age"""
self.name = name
self.age = age
def sit(self):
"""模擬小狗被命令時蹲下"""
print(self.name.title() + " is now sitting.")
def roll_over(self):
"""模擬小狗被命令時打滾"""
print(self.name.title() + " rolled over!")
方法__init__(),類在建立例項時,會自動執行__init__()方法
類中的所有方法引數必須有self,且在其他引數最前面,這樣例項才能夠訪問類中的屬性和方法
2.訪問類屬性
my_dog = Dog("willie",6)
print("My dog's name is "+ my_dog.name.title()+ ".")
print("My dog is " + str(my_dog.age) + "years old.")
#My dog's name is Willie.
#My dog is 6years old.
3.呼叫類方法
my_dog.sit()
my_dog.roll_over()
#Willie is now sitting.
#Willie rolled over!
4.繼承
class Car(object):
"""一次模擬汽車的簡單嘗試"""
def __init__(self, make, model, year):
self.make = make
self.model = model
self.year = year
self.odometer_reading = 0
def get_descriptive_name(self):
long_name = str(self.year) + ' ' + self.make + ' ' + self.model
return long_name.title()
def read_odometer(self):
print("This car has " + str(self.odometer_reading) + " miles on it.")
def update_odometer(self, mileage):
if mileage >= self.odometer_reading:
self.odometer_reading = mileage
else:
print("You can't roll back an odometer!")
def increment_odometer(self, miles):
self.odometer_reading += miles
def fill_gas_tank(self):
print ("This car need a gas tank!")
class ElectricCar(Car):
"""電動汽車的獨特之處"""
def __init__(self, make, model, year):
"""初始化父類的屬性"""
super(ElectricCar,self).__init__(make, model, year)
"""電動汽車特有屬性"""
self.battery_size = 70
"""電動汽車特有方法"""
def describe_battery(self):
"""列印一條描述電瓶容量的訊息"""
print("This car has a " + str(self.battery_size))
"""重寫父類方法"""
def fill_gas_tank(self):
print('重寫父類方法')
my_tesla = ElectricCar('tesla', 'models', 2016 )
print(my_tesla.get_descriptive_name())
my_tesla.describe_battery()
my_tesla.fill_gas_tank()
#2016 Tesla Models
#This car has a 70
#重寫父類方法
5.匯入模組中的類
建立animal.py檔案
class Cat():
def __init__(self):
print('建立貓例項')
class Dog():
def __init__(self):
print("建立狗例項")
建立index.py檔案
from animal import Cat,Dog
#或者 from animal import *
my_dog = Dog()
my_cat = Cat()
十. 檔案
1.從檔案中讀取資料
建立pi_digits.txt檔案
3.1415926535
8979323846
2643383279
建立file_reader.py檔案
with open('pi_digits.txt') as file_object:
contents = file_object.read()
print(contents)
#3.1415926535
# 8979323846
# 2643383279
逐行讀取—rstrip 可去除空白行
filename = 'pi_digits.txt'
with open(filename) as file_object:
for line in file_object:
print(line.rstrip())
#3.1415926535
# 8979323846
# 2643383279
2. 寫檔案,
開啟檔案時,可指定讀取模式 讀取模式 (‘r’ )、寫入模式 寫入模式 (‘w’ )、附加模式 附加模式 (‘a’ )或讓你能夠讀取和寫入檔案的模式(‘r+’ )。如果你省略了模式實參,Python將以預設的只讀模式開啟檔案。
filename = 'programming.txt'
with open(filename, 'w') as file_object:
file_object.write("I love programming.")