python文件读取---CSV文件的读取操作

#!/usr/bin/python
# -*- coding:utf-8 -*-

#1.当做普通文件直接读取
with open("123.csv","r",encoding="utf-8") as f:
    print(f.read()) #读取所有
    f.seek(0) #光标移动到最开始位置
    print(f.readline()) #读取一行
    print(f.readline(15)) #读取一行的前N个字符
    print(f.readlines()) #以列表形式读取每一行

#2.转换为csv对象读取
import csv
with open("123.csv","r",encoding="utf-8") as f:
    reader = csv.reader(f)
    for line in reader: #一行一行的读取，每一行都以列表形式存储
        print(line)

#3.转换为字典对象，按键值读取某一列
import csv
with open("123.csv","r",encoding="utf-8") as f:
    reader = csv.DictReader(f)
    for line in reader:
        print(dict(line),dict(line)["主观评分"])


#4.写入数据为一个header和一组values
import csv

header = ['name','age']
value1 = ['Tom',20]
value2 = ['张三',15]
value3 = [['李四',18],['王五','']]

with open('234.csv','a',newline='',encoding='utf-8-sig') as f:
    writer = csv.writer(f)
    writer.writerow(header) #一次写入一行
    writer.writerow(value1)
    writer.writerow(value2)
    writer.writerows(value3) #一次写入多行

#5.写入数据为字典
import csv

values = [{'name': 'jack', 'age': '15'},{'name': 'tom', 'age': '16'}]
header = list(values[0].keys()) #从字典数据中获取头部信息
with open("456.csv","a+",newline='',encoding="utf-8-sig") as f:
    writer = csv.DictWriter(f,header) #传2个参数，第一个参数为打开的.csv文件句柄，第二个参数为要写的表头
    writer.writeheader() #写入表头的专用方法，这里也可以使用writer.writerow(header)
    writer.writerows(values)