讀取、寫入文件 、存儲數據

1、讀取文件

一、讀取整個文件

file_name = 'cat.txt'

with open(file_name) as file_object:

　 contents = file_object.read()

　print(contents)　

二、逐行讀取，可以使用for循環

file_name = 'cat.txt'

with open(file_name) as file_object:

　　for line in file_object:

　　　　print(line.rstrip())

三、建立一個包含文件各行內容的列表

file_name = 'cat.txt'

with open(file_name) as file_object:

　　lines = file_object.readlines()

for line in lines:

　　print(line.rstrip())

四、使用文件的內容

file_name ='pi.txt'

with open(file_name) as file_object:

　　lines = file_object.readlines()

pi_string = ' '

for line in lines:

　　pi_string += line

print(pi_string)

2、寫入文件

一、‘w’寫入

with open(filename,'w') as file_object:

　　file_object.write(I want to hide")

注：寫入多行時後面須要加換行符。

二、‘a'附加　　

with open(filename,'a') as file_object:

　　file_object.write('I want to sleep')

3、異常

try-except-else

else在try代碼塊中執行成功時運行else代碼塊。

4、存儲數據

一、json.dump() 接受兩個實參，要存儲的數據，以及要存儲數據的文件類型

   json.load()接受一個實參，文件類型

二、如何用json.dump()來存儲列表

import json

numbers = [1,2,3,4,5,6]

filename = number.josn

with open(filename,'w') as file_object:

　　josn.dump(numbers,file_object)

三、保存和讀取用戶生成的數據

import json
file_name = 'number.json'
try:
    with open(file_name) as file_object:
        fav_number = json.load(file_object)

except:
    number = input("請輸入你喜歡的數字：")
    with open(file_name,'w') as file_object:
        fav_number = json.dump(number,file_object)
else:
    print("您最喜歡的數字是：%s" % fav_number)

四、重構

import json
file_name = 'username.json'
def got_name():
    """獲取用戶名稱"""
    try:
        with open(file_name) as file_object:
            user_name = json.load(file_object)
    except:
        return None
    else:
        return user_name

def new_name():
    """提醒用戶輸入名字"""
    user_name = input("請輸入您的名字：")
    with open(file_name,'w') as file_object:
        put_name = json.dump(user_name,file_object)
        return user_name


def greet():
    """向用戶發出問候"""
    username = got_name()
    if username:
        ask = input("用戶名是%s嗎?"%username)
        if ask == 'y':
            print("歡迎回來%s"%username)
        else:
            user_name =new_name()
            print("下次我會記得你哦！%s"%user_name)
    else:
        user_name = new_name()
        print("下次我會記得你哦！%s" % user_name)
greet()