python 读写csv文件 利用python 读写csv文件
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1、读文件
import csv
csv_reader = csv.reader(open("data.file", encoding="utf-8"))
for row in csv_reader:
print(row)
csv_reader把每一行数据转化成了一个list，list中每个元素是一个字符串。
2、写文件
读文件时，我们把csv文件读入列表中，写文件时会把列表中的元素写入到csv文件中。
list = ["1", "2", "3", "4"] out = open(outfile, "w") csv_writer = csv.writer(out) csv_writer.writerow(list)
可能遇到的问题：直接使用这种写法会导致文件每一行后面会多一个空行。
解决办法如下：
out = open(outfile, "w", newline="") csv_writer = csv.writer(out, dialect="excel") csv_writer.writerow(list)
在stackoverflow上找到了比较经典的解释，原来 python3里面对 str和bytes类型做了严格的区分，不像python2里面某些函数里可以混用。所以用python3来写wirterow时，打开文件不要用wb模式，只需要使用w模式，然后带上newline=''。
3、示例
- 简单读写
import csv
class writer:
def __init__(self):
self.dict = {
"标题": "标题",
"链接": "链接",
"服务": "服务",
"dsr": "dsr",
"店铺名": "店铺名",
"价格": "店铺名",
"付款人数": "付款人数",
"发货地": "发货地",
}
out = open("outfile.csv", "w", newline="")
self.csv_writer = csv.writer(out, dialect="excel")
self.csv_writer.writerow(self.dict)
def writer_to(self, key_value):
self.csv_writer.writerow(key_value)
if __name__ == "__main__":
a = writer()
new = {
"链接": "http://www.baidu.com",
"标题": "我是标题",
}
a.dict.update(new)
print(a.dict)
a.writer_to(a.dict.values())
- 结合爬虫
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("类目.csv", "w", newline="")
except PermissionError:
print("文件被其他程序占用")
input("")
csv_writer = csv.writer(out, dialect="excel")
csv_writer.writerow(["宝贝ID", "类目"])
def open_chrome():
driver[0] = webdriver.Chrome()
driver[0].get("https://www.dianchacha.com")
input("请登陆后按回车:")
def EC_located(one_group, value):
"""
目的：简化代码长度，参数1选择one或者group切换选中模式
:param value:要找的值【CSS选择器】
:return:选择到的对象
"""
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元素未加载成功，等待超时")
else:
try:
ecl = wait.until(
EC.presence_of_all_elements_located((By.CSS_SELECTOR, value))
)
return ecl
except TimeoutException:
print(value, "1元素---组---未加载成功，等待超时")
def operating(ID):
# 先获取ID输入框
driver[0].get("https://www.dianchacha.com/item/info/index/iid/" + ID)
html = driver[0].page_source
if "未能找到亲的宝贝" not in html:
colspans = EC_located("group", ".colspan-1")
colspan[0] = str(colspans[1].text).replace("宝贝类目： ", "")
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 = "宝贝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()
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