Python：よく使うコードまとめ

import pandas as pd

def b4_day_close( df ) :
  b4_date, b4_close, day_close = None, None, None
  def apply_logic( row ):
    nonlocal b4_date, b4_close, day_close
    today, hour = row.name, row.name.hour
    diff_seconds = ( today - b4_date ).seconds if b4_date else None
    if diff_seconds and diff_seconds > 60 and hour == 16 :
      day_close = b4_close
    b4_date, b4_close = today, row["c"]
    return day_close
  return apply_logic

df['b4_day_c'] = df.apply( b4_day_close( df ), axis=1 )

import pandas as pd

dt={ "x": [ 1100, 1200, 1300 ],
     "y": [ 2100, 2200, 2300 ], }
df = pd.DataFrame(dt)

def fnc( df ) :
    return df["x"]+1,df["x"]+2

df[["a","b"]] = df.apply( fnc( df ), axis=1, result_type='expand' )

import pandas as pd

df_l = _get_df( "N225f", year )
df_r = _get_df( "Topixf", year )
df = df_l.join( df_r, lsuffix="_n", rsuffix="_t" )

import pandas as pd
import datetime as dt

def _get_df( symbol, year ) :
  df = pd.read_excel( f'{BASEDIR}/{symbol}_{year}.xlsx',
                     names=("date","time","open","high","low","close","volume"),
                     sheet_name='1min' )
  df["time"] = df["time"].astype( str )
  df["Datetime"] = pd.to_datetime( df["date"].dt.strftime("%x ") + df["time"] )
  # Datetime：取引日（営業日） → カレンダーの調整
  df.loc[ df["time"]>="16:30:00", "Datetime" ] = df.loc[ df["time"]>="16:30:00", "Datetime" ] + dt.timedelta( days=-1 )
  df = df.set_index("Datetime")

import datetime as dt
sample_datetime + dt.timedelta( days=-1 )

import pandas as pd
diff_seconds = ( this_datetime - b4_datetime ).seconds