Python Panda 的 Write CSV - Append vs. Write
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Panda's Write CSV - Append vs. Write
提问by GPB
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:
如果“文件名”不存在，我想使用 pd.write_csv 写入“文件名”（带标题），否则附加到“文件名”（如果存在）。如果我只是使用命令：
df.to_csv('filename.csv',mode = 'a',header ='column_names')
The write or append succeeds, but it seems like the header is written every time an append takes place.
写入或追加成功，但似乎每次追加发生时都会写入标头。
How can I only add the header if the file doesn't exist, and append without header if the file does exist?
如果文件不存在，如何仅添加标题，如果文件存在，如何不添加标题？
采纳答案by Padraic Cunningham
Not sure there is a way in pandas but checking if the file exists would be a simple approach:
不确定大熊猫有没有办法，但检查文件是否存在将是一种简单的方法：
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)
回答by user3657041
with open(filename, 'a') as f:
df.to_csv(f, mode='a', header=f.tell()==0)
it will add header when writes to the file first time
第一次写入文件时它会添加标题
回答by VK Singh
In Pandas dataframe "to_csv" function, use header=False if csv file exists & append to existing file.
在 Pandas 数据框“to_csv”函数中，如果 csv 文件存在并附加到现有文件，则使用 header=False。
import os
hdr = False if os.path.isfile('filename.csv') else True
df.to_csv('filename.csv', mode='a', header=hdr)
