[英]How to copy rows from multiple csv files to new files in pandas?
我有10個csv文件。 我想從所有csv文件中復制第一行並保存為新的csv文件,然后從所有csv文件中復制第二行並保存為第二個csv文件等。以下我的代碼僅針對第一行和其他rwos顯示NaN
。 我的錯誤在哪里?
碼
import pandas as pd
import datetime
import glob
path = r'/Jupyter_Works/new_csv'
all_files = glob.glob(path + "/*.csv")
date_time = datetime.datetime(2018, 1, 1)
index = pd.date_range(start='1/1/2018', periods= 8760, freq='H')
columns = ['Lat','Lon','Alt','Temperature','Relative Humidity','Wind speed','Wind direction','Short-wave irradiation']
dfcsv = pd.DataFrame(index=index, columns=columns)
for filename in all_files:
df = pd.read_csv(filename, index_col='time', header=0)
dfcsv.iloc[0] = df.iloc[0]
dfcsv
結果
Lat Lon Alt Temperature Relative Humidity Wind speed Wind direction Short-wave irradiation
2018-01-01 00:00:00 31.03 49.36 99 285.56 52.82 2.95 128.5 0
2018-01-01 01:00:00 NaN NaN NaN NaN NaN NaN NaN NaN
2018-01-01 02:00:00 NaN NaN NaN NaN NaN NaN NaN NaN
2018-01-01 03:00:00 NaN NaN NaN NaN NaN NaN NaN NaN
2018-01-01 04:00:00 NaN NaN NaN NaN NaN NaN NaN NaN
首先創建一個帶有列表理解和concat
大型DataFrame
,按照loc
選擇的唯一值循環,並通過DataFrame.to_csv
寫入文件。 它工作,因為每個DataFrame都有唯一索引,因此如果按唯一值選擇,則選擇所有文件中具有相同位置的行。
path = r'/home/nickan/Jupyter_Works/new_csv'
all_files = glob.glob(path + "/*.csv")
dfs = [pd.read_csv(fp, index_col='time', parse_dates=['time']) for fp in all_files]
df = pd.concat(dfs)
for x in df.index.unique():
#removed duplicated index by index=False
df.loc[x].to_csv(f'csv/file_{x.strftime("%Y-%m-%d_%H")}.csv', index=False)
編輯:
因為內存問題是可能的,所以使用dataFrames中每行循環的替代解決方案並以append模式寫入:
for i, fp in enumerate(all_files):
df = pd.read_csv(fp, index_col='time', parse_dates=['time'])
for x in df.index:
f = f'out/file_{x.strftime("%Y-%m-%d_%H")}.csv'
if i == 0:
df.loc[[x]].to_csv(f, index=False)
else:
df.loc[[x]].to_csv(f, index=False,header=None, mode='a')
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