利用python 读写csv文件
作者:新码农
python中有一个读写csv文件的包,直接import csv即可。利用这个python包可以很方便对csv文件进行操作。
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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