Panda 的 Write CSV - Append vs. Write [英] Panda's Write CSV - Append vs. Write

问题描述

如果filename"不存在，我想使用 pd.write_csv 写入filename"(带标题)，否则附加到filename"(如果存在).如果我只是使用命令:

I would like to use pd.write_csv to write "filename" (with headers) if "filename" doesn't exist, otherwise to append to "filename" if it exists. If I simply use command:

     df.to_csv('filename.csv',mode = 'a',header ='column_names')

写入或追加成功，但似乎每次追加发生时都会写入标头.

The write or append succeeds, but it seems like the header is written every time an append takes place.

如果文件不存在，我如何只添加标题，如果文件存在，我如何不添加标题?

How can I only add the header if the file doesn't exist, and append without header if the file does exist?

推荐答案

不确定 Pandas 有没有办法，但检查文件是否存在是一个简单的方法:

Not sure there is a way in pandas but checking if the file exists would be a simple approach:

import os
# if file does not exist write header 
if not os.path.isfile('filename.csv'):
   df.to_csv('filename.csv', header='column_names')
else: # else it exists so append without writing the header
   df.to_csv('filename.csv', mode='a', header=False)

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