By default to_csv writes a CSV like
,a,b,c 0,0.0,0.0,0.0 1,0.0,0.0,0.0 2,0.0,0.0,0.0
But I want it to write like this:
a,b,c 0,0.0,0.0,0.0 1,0.0,0.0,0.0 2,0.0,0.0,0.0
How do I achieve this? I can’t set index=False because I want to preserve the index. I just want to remove the leading comma.
df = pd.DataFrame(np.zeros((3,3)), columns = ['a','b','c'])
df.to_csv("test.csv") # this results in the first example above.
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Answer
It is possible by write only columns without index first and then data without header in append mode:
df = pd.DataFrame(np.zeros((3,3)), columns = ['a','b','c'], index=list('XYZ'))
pd.DataFrame(columns=df.columns).to_csv("test.csv", index=False)
#alternative for empty df
#df.iloc[:0].to_csv("test.csv", index=False)
df.to_csv("test.csv", header=None, mode='a')
df = pd.read_csv("test.csv")
print (df)
a b c
X 0.0 0.0 0.0
Y 0.0 0.0 0.0
Z 0.0 0.0 0.0