text: import numpy as np
  import pandas as pd
  from pandas import NaT
  
  from trading_calendars import TradingCalendar
  
  from zipline.data.bar_reader import OHLCV, NoDataOnDate, NoDataForSid
  from zipline.data.session_bars import CurrencyAwareSessionBarReader
  from zipline.utils.input_validation import expect_types, validate_keys
  from zipline.utils.pandas_utils import check_indexes_all_same
  
  
  class InMemoryDailyBarReader(CurrencyAwareSessionBarReader):
      """
      A SessionBarReader backed by a dictionary of in-memory DataFrames.
  
      Parameters
      ----------
      frames : dict[str -> pd.DataFrame]
          Dictionary from field name ("open", "high", "low", "close", or
          "volume") to DataFrame containing data for that field.
      calendar : str or trading_calendars.TradingCalendar
          Calendar (or name of calendar) to which data is aligned.
      currency_codes : pd.Series
          Map from sid -> listing currency for that sid.
      verify_indices : bool, optional
          Whether or not to verify that input data is correctly aligned to the
          given calendar. Default is True.
      """
      @expect_types(
          frames=dict,
          calendar=TradingCalendar,
          verify_indices=bool,
          currency_codes=pd.Series,
      )
      def __init__(self,
                   frames,
                   calendar,
                   currency_codes,
                   verify_indices=True):
          self._frames = frames
          self._values = {key: frame.values for key, frame in frames.items()}
          self._calendar = calendar
          self._currency_codes = currency_codes
  
          validate_keys(frames, set(OHLCV), type(self).__name__)
          if verify_indices:
              verify_frames_aligned(list(frames.values()), calendar)
  
          self._sessions = frames['close'].index
          self._sids = frames['close'].columns
  
      @classmethod
      def from_panel(cls, panel, calendar, currency_codes):
          """Helper for construction from a pandas.Panel.
          """
          return cls(dict(panel.iteritems()), calendar, currency_codes)
  
      @property
      def last_available_dt(self):
          return self._calendar[-1]
  
      @property
      def trading_calendar(self):
          return self._calendar
  
      @property
      def sessions(self):
          return self._sessions
  
      def load_raw_arrays(self, columns, start_dt, end_dt, assets):
          if start_dt not in self._sessions:
              raise NoDataOnDate(start_dt)
          if end_dt not in self._sessions:
              raise NoDataOnDate(end_dt)
  
          asset_indexer = self._sids.get_indexer(assets)
          if -1 in asset_indexer:
              bad_assets = assets[asset_indexer == -1]
              raise NoDataForSid(bad_assets)
  
          date_indexer = self._sessions.slice_indexer(start_dt, end_dt)
  
          out = []
          for c in columns:
              out.append(self._values[c][date_indexer, asset_indexer])
  
          return out
  
      def get_value(self, sid, dt, field):
          """
          Parameters
          ----------
          sid : int
              The asset identifier.
          day : datetime64-like
              Midnight of the day for which data is requested.
          field : string
              The price field. e.g. ('open', 'high', 'low', 'close', 'volume')
  
          Returns
          -------
          float
              The spot price for colname of the given sid on the given day.
              Raises a NoDataOnDate exception if the given day and sid is before
              or after the date range of the equity.
              Returns -1 if the day is within the date range, but the price is
              0.
          """
          return self.frames[field].loc[dt, sid]
  
      def get_last_traded_dt(self, asset, dt):
          """
          Parameters
          ----------
          asset : zipline.asset.Asset
              The asset identifier.
          dt : datetime64-like
              Midnight of the day for which data is requested.
  
          Returns
          -------
          pd.Timestamp : The last know dt for the asset and dt;
                         NaT if no trade is found before the given dt.
          """
          try:
              return self.frames['close'].loc[:, asset.sid].last_valid_index()
          except IndexError:
              return NaT
  
      @property
      def first_trading_day(self):
          return self._sessions[0]
  
      def currency_codes(self, sids):
          codes = self._currency_codes
          return np.array([codes[sid] for sid in sids])
  
  
  def verify_frames_aligned(frames, calendar):
      """
      Verify that DataFrames in ``frames`` have the same indexing scheme and are
      aligned to ``calendar``.
  
      Parameters
      ----------
      frames : list[pd.DataFrame]
      calendar : trading_calendars.TradingCalendar
  
      Raises
      ------
      ValueError
          If frames have different indexes/columns, or if frame indexes do not
          match a contiguous region of ``calendar``.
      """
      indexes = [f.index for f in frames]
      check_indexes_all_same(indexes, message="DataFrame indexes don't match:")
  
      columns = [f.columns for f in frames]
      check_indexes_all_same(columns, message="DataFrame columns don't match:")
  
      start, end = indexes[0][[0, -1]]
      cal_sessions = calendar.sessions_in_range(start, end)
  
      check_indexes_all_same(
          [indexes[0], cal_sessions],
          f"DataFrame index doesn't match {calendar.name} calendar:",
      )
  