对文件操作，对数据做运算

'''
1. 文件test.txt内容：每一行内容分别为商品名字，价钱，个数，求出本次购物花费的总钱数
使用列表解析，从文件a.txt中取出每一行，做成下述格式：[{‘name’:'apple','price':10,'count':3},{...},{...},...]
apple 10 3
tesla 100000 1
mac 3000 2
lenovo 30000 3
chicken 10 3


'''
# f = open('test.txt','r',encoding='utf-8')
# set = []
# l = f.readline().split()
# print(l)
# set.append({'name':l[0],'price':l[1],'count':l[2]})
# print(set)

# 1、
goods_info=[]
with open('test.txt','r') as f:
    for line in f:
        l = line.split()
        goods_info.append({'name':l[0],'price':int(l[1]),'count':int(l[2])})
    ll = list(map(lambda x:x['price']*x['count'],goods_info))
    ss = sum(ll)
    print(ll)
    print(ss)
print(goods_info) # [{'name': 'apple', 'price': 10, 'count': 3}, {'name': 'tesla', 'price': 100000, 'count': 1}, {'name': 'mac', 'price': 3000, 'count': 2}, {'name': 'chicken', 'price': 200, 'count': 3}]

'''
2. 修改文件内容，把文件中的alex都替换成SB
'''
# 2、
import os

with open('a.txt','r',encoding='utf-8') as read_f, open('.a.txt.swap','w',encoding='utf-8') as write_f:
    for line in read_f:
        line = line.replace('alex','SB')
        write_f.write(line)

os.remove('a.txt')
os.rename('.a.txt.swap','a.txt')