python for循环写入csv表格添加数据的时候会被最后的数据覆盖

Question

在爬虫或者数据分析过程中，使用for循环添加的数据被最后一次循环覆盖参数

如下尝试其他博主的方式也没有改变。

for的循环写入不被覆盖需要用‘a’写入方法，我原来用的‘w’所以被覆盖了

filename = 'allserver.txt' 
with open(filename,'a',encoding='utf-8') as f: 
    f.writelines(dates + '*'*50 + '\n')

我需要的操作是提取每一合约 进行数据分析

for循环代码如下：

import pandas as pd
data=pd.read_csv(r"/Users/bingtangdunxueli期货交易记录.csv",encoding="gbk")
for i in data["合约"]:
    print(i)
    data_gender = data[['日期','品种','合约','合约乘数','买开手数','买开均价']]
    data_gender_re = data_gender[data_gender.notnull()]
    FF = data_gender_re.loc[(data_gender_re['合约'] == i)]
    filename = '/Users/bingtangdunxueli/quanbu.csv'
    with open(filename,'a',encoding='utf-8') as f:
       f.writelines(FF)

结果仍然是最后数据覆盖

 

 

Answer 1

import pandas as pd
data=pd.read_csv(r"/Users/bingtangdunxueli期货交易记录.csv",encoding="gbk")
filename = '/Users/bingtangdunxueli/quanbu.csv'
with open(filename,'w',encoding='utf-8') as f:
    f.write("日期,品种,合约,合约乘数,买开手数,买开均价\n")
    for i in data["合约"]:
        print(i)
        data_gender = data[['日期','品种','合约','合约乘数','买开手数','买开均价']]
        data_gender_re = data_gender[data_gender.notnull()]
        FF = data_gender_re.loc[(data_gender_re['合约'] == i)]
        for li in FF.values.tolist():
            s = ",".join(map(str,li))
            f.write(s+"\n")

这样看看