new_contents: import pandas as pd
  import numpy as np
  import os
  import glob
  
  def cleancsv(source, destination):
      """Removes duplicates,forward fills the missing values based on date attribute
      from the source data and saves it to destination path."""
  
      try:
          data = pd.read_csv(source,parse_dates=True)
      except (FileNotFoundError, IOError):
          print('Wrong file or file path.')
          return
      if data.empty:
          return
  
      data  = data.drop_duplicates(subset = 'Date', keep='first')
  
      data = data.set_index(pd.DatetimeIndex(data.Date))
  
      idx = pd.date_range(data.index.min(), data.index.max())
      indexed_data = data.reindex(index = idx, fill_value = np.nan)
      indexed_data = indexed_data.replace('0', np.nan)
      indexed_data = indexed_data.fillna(method='ffill')
      indexed_data = indexed_data.drop('Date', 1)
  
      indexed_data.to_csv(destination, index_label='Date')
      return
  
  def cleanall(source, destination='../cleaneddata/'):
      """Performs data cleaning on all .csv files present on the source directory and
      saves each file in destination folder."""
  
      if not os.path.exists(destination):
          os.makedirs(destination)
  
      os.chdir(source)
      for file in glob.glob("*.csv"):
          filename = os.path.basename(file)
          print('Cleaning'+filename+'...\n')
          cleancsv(file, destination+filename)
      return
  
  cleanall('../data')
  
subject: Add data cleaning module