python3讀寫csv文件

python讀取CSV文件

 

python中有一個讀寫csv文件的包，直接import csv便可。利用這個python包能夠很方便對csv文件進行操做，一些簡單的用法以下。

1. 讀文件

csv_reader = csv.reader(open('data.file', encoding='utf-8'))
for row in csv_reader:
    print(row)

例若有以下的文件

輸出結果以下

['0.093700','0.139771','0.062774','0.007698']

['-0.022711','-0.050504','-0.035691','-0.065434']

['-0.090407','0.021198','0.208712','0.102752']

['-0.085235','0.009540','-0.013228','0.094063']

可見csv_reader把每一行數據轉化成了一個list，list中每一個元素是一個字符串。

2. 寫文件

讀文件時，咱們把csv文件讀入列表中，寫文件時會把列表中的元素寫入到csv文件中。

list = ['1', '2','3','4']
out = open(outfile, 'w')
csv_writer = csv.writer(out)
csv_writer.writerow(list)

可能遇到的問題：直接使用這種寫法會致使文件每一行後面會多一個空行。

解決辦法以下：

out = open(outfile, 'w', newline='')
csv_writer = csv.writer(out, dialect='excel')
csv_writer.writerow(list)

參考以下：

在stackoverflow上找到了比較經典的解釋，原來 python3裏面對 str和bytes類型作了嚴格的區分，不像python2裏面某些函數裏能夠混用。因此用python3來寫wirterow時，打開文件不要用wb模式，只須要使用w模式，而後帶上newline=''。 

3down vote

In Python 2.X, it was required to open the csvfile with 'b' because the csv module does its own line termination handling. In Python 3.X, the csv module still does its own line termination handling, but still needs to know an encoding for Unicode strings. The correct way to open a csv file for writing is: outputfile=open("out.csv",'w',encoding='utf8',newline='') encoding can be whatever you require, but newline='' suppresses text mode newline handling. On Windows, failing to do this will write \r\r\n file line endings instead of the correct \r\n. This is mentioned in the 3.X csv.reader documentation only, but csv.writer requires it as well.

連接：http://blog.csdn.net/lixiang0522/article/details/7755059

 

 

 1 class writer():
 2     def __init__(self):
 3         self.dict={
 4             "標題":"標題",
 5             "連接":"連接",
 6             "服務":"服務",
 7             "dsr":"dsr",
 8             "店鋪名":"店鋪名",
 9             "價格":"店鋪名",
10             "付款人數":"付款人數",
11             "發貨地":"發貨地"
12         }
13         out = open("outfile.csv", 'w', newline='')
14         self.csv_writer = csv.writer(out, dialect='excel')
15         self.csv_writer.writerow(self.dict)
16 
17     def writer_to(self,key_value):
18         self.csv_writer.writerow(key_value)
19 
20 
21 if __name__ == '__main__':
22     a=writer()
23     new={"連接":"http://www.baidu.com",'標題':'我是標題',}
24     a.dict.update(new)
25     print(a.dict)
26     a.writer_to(a.dict.values())

類

 

import csv

from selenium import webdriver
from selenium.webdriver.common.by import By
from selenium.webdriver.support.ui import WebDriverWait
from selenium.webdriver.support import expected_conditions as EC
from selenium.common.exceptions import TimeoutException, NoSuchElementException
from selenium.webdriver.common.action_chains import ActionChains

driver=['1','2']
colspan=['1','2']
try:
    out = open('類目.csv', 'w', newline='')
except PermissionError:
    print('文件被其餘程序佔用')
    input('')
csv_writer = csv.writer(out, dialect='excel')
csv_writer.writerow(['寶貝ID','類目'])




def open_chrome():
    driver[0]=webdriver.Chrome()
    driver[0].get('https://www.dianchacha.com')
    input('請登錄後按回車:')





def EC_located(one_group,value):
    '''
     目的：簡化代碼長度，參數1選擇one或者group切換選中模式
    :param value:要找的值【CSS選擇器】
    :return:選擇到的對象
    '''
    wait = WebDriverWait(driver[0], 10)
    if one_group=="one":
        try:
            ecl=wait.until(EC.presence_of_element_located((By.CSS_SELECTOR,value)))
            return ecl
        except TimeoutException:
            print(value,'1元素未加載成功，等待超時')
    else:
        try:
            ecl=wait.until(EC.presence_of_all_elements_located((By.CSS_SELECTOR,value)))
            return ecl
        except TimeoutException:
            print(value,'1元素---組---未加載成功，等待超時')


def operating(ID):
    #先獲取ID輸入框
    driver[0].get('https://www.dianchacha.com/item/info/index/iid/'+ID)
    html=driver[0].page_source
    if '未能找到親的寶貝' not in html:
        colspans=EC_located('group','.colspan-1')
        colspan[0]=str(colspans[1].text).replace('寶貝類目： ','')
    else:
        return operating(ID)
    print(colspan)


def writer_txt():
    csv_writer.writerow([url[0],colspan[0]])
    print('保存',url[0],colspan[0],'成功')

url=['0','1']
def main():
    open_chrome()
    file = '寶貝ID.txt'
    with open(file) as f:
        for line in f.readlines():
            url[0] = line
            print(line)
            operating(url[0])
            writer_txt()
        out.close()
        print('已完成')





if __name__ == '__main__':
    main()

讀文本寫csv