python3读/写文件,读csv

用Python 内构函数open来写入字符串到txt文件里

text = 'now ,we\'re  write into the file'
'''
调用buid-in函数，open打开或创建文件
如果file不存在，就自动创建，w 写的模式，r读的模式
'''

file = open(r'E:\toolsd\pythoncode\example.txt','w')
file.write(text)
file.close()
readtxt = open('example.txt','r').read()

print(readtxt)
'''
file = open(r'E:\toolsd\pythoncode\example.txt','w')指定了文件的路径，
若直接 file = open('example.txt','w'),则文件在当前的.py文件下
文件路径前面的 ‘r’ 表示不需要转义，原义输出，因为上面有\，反斜杠默认是转义，所以需要添加r
输出效果
'''

读csv,逗号分隔符
主要有read和write两个功能
1、先创建一个csv文件，直接将txt的后缀改为csv即可。例如数据如下

"Year", "Country","Sex","Name"
"2001","China","Male","Bob"
"2002","UK","F","Bonny"
"2003","US","M","王军"
"2004","South Korea","M","Tom"
"2005","Japan","F","Alicia"
"2019","Germany","M","Robbin"

2、csv文件直接放在当前.py的路径下面

3、demo.py

import csv

with open('example.csv','r') as csvfile:
    readCSV = csv.reader(csvfile)
    for row in readCSV:
        print(row)

结果：

image.png 4、进入到指定的某列

import csv

with open('example.csv','r') as csvfile:
    readCSV = csv.reader(csvfile)
    for row in readCSV:
        #print(row)
        print(row[0])
       # print(row[1],row[0])

结果：

image.png 5、单独输出每列

import csv
with open('example.csv','r') as csvfile:
    readCSV = csv.reader(csvfile)
    years =[]
    countys =[]
    sexs = []
    for row in readCSV:
        year = row[0]
        county = row[1]
        sex = row[2]

        years.append(year)
        countys.append(county)
        sexs.append(sex)
    print(years)
    print(countys)
    print(sexs)

结果： image.png