python对csv文件追加写入列的方法

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import pandas as pd
import numpy as np
data = pd.read_csv(r'平均值.csv')
print(data.columns)#获取列索引值
data1 = data['flow']#获取列名为flow的数据作为新列的数据
data['cha'] = data1 #将新列的名字设置为cha
data.to_csv(r"平均值12.csv",mode = 'a',index =False)
#mode=a，以追加模式写入,header表示列名，默认为true,index表示行名，默认为true，再次写入不需要行名
print(data)

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with open(os.path.join(os.path.dirname(__file__), "file1")) as csvFile:
  rows = csv.reader(csvFile)
  with open(os.path.join(os.path.dirname(__file__), "file2"), 'w') as f:
    writer = csv.writer(f)
    for row in rows:
      row.append(“123465”)
      writer.writerow(row)