import os from .__init__ import Reader,Writer import json class DiskReader(Reader) : """ This class is designed to read data from disk (location on hard drive) @pre : isready() == True """ def __init__(self,**params): """ @param path absolute path of the file to be read """ Reader.__init__(self) self.path = params['path'] ; self.delimiter = params['delimiter'] if 'delimiter' in params else None def isready(self): return os.path.exists(self.path) def read(self,size=-1): """ This function reads the rows from a designated location on disk @param size number of rows to be read, -1 suggests all rows """ f = open(self.path,'rU') i = 1 for row in f: i += 1 if size == i: break if self.delimiter : yield row.split(self.char) yield row f.close() class DiskWriter(Writer): """ This function writes output to disk in a designated location. The function will write a text to a text file - If a delimiter is provided it will use that to generate a xchar-delimited file - If not then the object will be dumped as is """ def __init__(self,**params): Writer.__init__(self) self.cache['meta'] = {'cols':0,'rows':0,'delimiter':None} if 'path' in params: self.path = params['path'] else: self.path = 'data-transport.log' self.delimiter = params['delimiter'] if 'delimiter' in params else None # if 'name' in params: # self.name = params['name']; # else: # self.name = 'data-transport.log' # if os.path.exists(self.path) == False: # os.mkdir(self.path) def meta(self): return self.cache['meta'] def isready(self): """ This function determines if the class is ready for execution or not i.e it determines if the preconditions of met prior execution """ return True # p = self.path is not None and os.path.exists(self.path) # q = self.name is not None # return p and q def format (self,row): self.cache['meta']['cols'] += len(row) if isinstance(row,list) else len(row.keys()) self.cache['meta']['rows'] += 1 return (self.delimiter.join(row) if self.delimiter else json.dumps(row))+"\n" def write(self,info): """ This function writes a record to a designated file @param label @param row row to be written """ f = open(self.path,'a') f.write(self.format(info)) f.close()