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+--- Thread: [Solved] df.loc: write data in certain rows (/thread-34068.html)
[Solved] df.loc: write data in certain rows - ju21878436312 - Jun-28-2021
I import a text file and would like to write a comment in certain rows, which I access with df.loc.
However, I get the error "# When setting, missing keys are not allowed, even with .loc:".
Could someone tell me, how to avaid it? I have checked the documentation, where a similar way worked out .
import pandas as pd
import numpy as np
df = pd.read_csv('2021-06-15_data.txt', delimiter= '\t',parse_dates=[[0, 1]], header=None, names=["Date","Time","Channel","time","0.3","0.5","1.0","3.0","5.0","10.0"])
df['Date_Time'] = df['Date_Time'] + pd.Timedelta(days = 365*20)
# print types works fine
print(df.head(5))
df.dtypes
# iloc works fine
print("iloc")
df.iloc[5:7]
# loc works fine
print("loc")
df.loc[(df['Date_Time'] >= '2021-06-10 09:51:04')&(df['Date_Time'] < '2021-06-10 09:51:26')]
# create new column
df['Comment']=""
# write data in column 'Comment', only for certain rows creates KeyError
df.loc[(df['Date_Time'] >= '2021-06-10 09:51:04')&(df['Date_Time'] < '2021-06-10 09:51:26'),df['Comment']]="zero"2021-06-15_data.txt: 15.06.2001 09:50:42 1 10 5 4 4 1 1 1 15.06.2001 09:50:53 1 10 0 0 0 0 0 0 15.06.2001 09:51:04 1 10 0 0 0 0 0 0 15.06.2001 09:51:15 1 10 0 0 0 0 0 0 15.06.2001 09:51:26 1 10 0 0 0 0 0 0 15.06.2001 09:51:37 1 10 0 0 0 0 0 0 15.06.2001 09:51:48 1 10 0 0 0 0 0 0 15.06.2001 09:51:59 1 10 0 0 0 0 0 0 15.06.2001 09:52:10 1 10 0 0 0 0 0 0 15.06.2001 09:52:21 1 10 0 0 0 0 0 0
RE: df.loc: write data in certain rows - ju21878436312 - Jun-28-2021
I found the solution:
# write data in column 'Comment', only for certain rows creates KeyError df.loc[(df['Date_Time'] >= '2021-06-10 09:50:31')&(df['Date_Time'] < '2021-06-10 09:51:00'),'Comment']="zero" df