務必注意讀/寫方式和指針位置

1、文件操作總結
模式'r'或者‘r+’或者‘rb+’指針初始位置在文件開頭
模式'w'或者‘w+’或者‘wb+’指針初始位置在文件末尾
模式'a'或者‘a+’或者‘ab+’指針初始位置在文件末尾

模式'w'或者‘w+’或者‘wb+’,新創(chuàng)建文件，會覆蓋原文件，慎用
file.truncate(20)，文件從0開始只保留20個字符，其余被清除，慎用
file.readlines()，比較占用資源，對于大文件，盡量不用
file.flush()，強制刷新新寫入內容至磁盤

2、文件練習：

__author__ = 'admin' f = open('file1','r+',encoding='utf-8')print(f.write('Yello++++'))''' import sys,timefor i in range(10):sys.stdout.write('#')sys.stdout.flush()time.sleep(0.2) f = open('file1','ab+') f.seek(0) print(f.readline()) print(f.readline()) print('\n=====\n') f.write('hello binary'.encode())print(f.readline()) print(f.tell()) print(f.readline()) print(f.tell()) f.seek(60) print(f.tell()) print(f.readline()) print() #print(f.write('\nhello ---====----'))count = 0 for line in f :if count ==9 :print(f.write('this is an insert message'))count +=1continueprint(f.readline())count +=1 '''

3、購物車練習：
readme:商品列表寫在文件goods_list中,以只讀方式打開，讀取第一行，使用eval()函數(shù)轉變?yōu)榱斜?#xff1b;先以只讀方式打開username_info文件，eval（）讀取字典方式記錄的{‘username’:[[選購清單]，余額]}信息,關閉文件；提示輸入用戶名，判斷用戶名是否在username_info中，如果在，直接讀取shopping_l 和salary；如果不在，則提示輸入salary，然后選購，然后字典添加{‘username’:[[選購清單]，余額]}，最后寫入信息，覆蓋原先的'username_info'文件

__author__ = 'Administrator' username = input('Please input your username:') #f_n = open('usernamelist','r+',encoding='utf-8') f_n_info = open('username_info','r',encoding='utf-8') salary = 0 goods_f = open('goods_list','r',encoding='utf-8') goods_l = eval(goods_f.readline()) goods_f.close() shopping_l = [] for index, item in enumerate(goods_l,0):print(index,item)def print_shopping():print('----shopping list----')for i in shopping_l :print(i)print('Your current balance is :',salary)f_dict[username] =[shopping_l,salary]f_new_info = open('username_info','w+',encoding='utf-8')f_new_info.write(str(f_dict))f_new_info.close()exit()f_dict = eval(f_n_info.readline()) f_n_info.close() if username in f_dict.keys() :shopping_l =f_dict[username][0]salary = f_dict[username][1]print(shopping_l,'\n',salary) else:salary = input('Please input your salary:')if salary.isdigit() :salary = int(salary)while True :choice = input('Please input the goods number (%s-%s):'%(0,len(goods_l)))if choice.isdigit() :choice = int(choice)if choice < len(goods_l) and choice >= -1 :p_item = goods_l[choice]if p_item[1] <= salary :shopping_l.append(p_item[0])salary -= p_item[1]print('Add %s into your shopping cart,your current balance is:\033[31;1m %s\033[0m '%(p_item[0],salary))else :print('You have no enough money.')print_shopping()else :print('Invalid number,please input again.')elif choice == 'q'or choice == 'Q' :print_shopping()# print('----shopping list----')# for i in shopping_l :# print(i)# print('Your current balance is :',salary)# exit()else:print('Invalid input,please input a number.')else:print('Invalid input')#for i in goods_l : # print(goods_l.index(i),i)

轉載于:https://www.cnblogs.com/chongmao/p/9870349.html

與50位技術專家面對面20年技術見證，附贈技術全景圖

總結

以上是生活随笔為你收集整理的python 入门第二课2 file的文件操作的全部內容，希望文章能夠幫你解決所遇到的問題。

如果覺得生活随笔網(wǎng)站內容還不錯，歡迎將生活随笔推薦給好友。