val1,val2,val3
aa,bb,cc
a
a,bb,cc
aa
,bb,cc
aa,
bb,cc
a\a,bb,cc

val1,val2,val3
aa,bb,cc
aa,bb,cc
aa,bb,cc
aa,bb,cc
aa,bb,cc

# -*- coding: utf-8 -*-
# Author AnJia(anjia0532@gmail.com https://anjia0532.github.io)
import argparse
import sys, os
import io
reload(sys)
sys.setdefaultencoding('utf8')
black_dict={"\\":"","\"":""}
def main():
  parser = argparse.ArgumentParser()
  parser.add_argument('--cols', type=int, dest='cols', action='store', default=-1,help="count of columns,default first line's cells")
  parser.add_argument('--src', type=str, dest='src', action='store', default='',
            help='path to source csv file')
  parser.add_argument('--dest', type=str, dest='dest', action='store', default='',
            help='path to dest csv file')
  parser.add_argument('--encoding', type=str, dest='encoding', action='store', default='utf-8',
            help='file encoding,default utf-8')
  parser.add_argument('--chunksize', type=int, dest='chunksize', action='store', default='10000',
            help='batch lines to write dest file,default 10000')
  parser.add_argument('--delimiter', type=str, dest='delimiter', action='store', default=',',
            help='csv delimiter,default ,')
  args = parser.parse_args()
  cols = args.cols
  src = args.src
  dest = args.dest
  encoding = args.encoding
  chunksize = args.chunksize
  delimiter = args.delimiter
  if not (src and dest) or chunksize <= 0:
   print("invaild args!") 
   sys.exit(-1)
  olds=[]
  lines=[]
  with io.open(src,encoding=encoding) as fp:
   for line in fp.readlines():
    line = line.strip()
    for k,v in black_dict.items():
     if k in line:
      line=line.replace(k,v)
    cells = line.split(delimiter)
    if cols == -1:
     cols=len(cells)
    if(len(cells) < cols or (len(olds)>0 and len(olds) < cols)):
     if not olds:
      olds = cells
     else:
      cells[0]=olds[-1]+cells[0]
      olds.pop()
      olds.extend(cells)
    if len(olds) >= cols:
     cells=olds
     olds=[]
    if not olds:
     lines.append(delimiter.join(cells[0:cols])+"\n")
    if len(lines) % chunksize == 0:
     write_to_file(dest=dest,lines=lines)
     lines=[]
   write_to_file(dest=dest,lines=lines)
def write_to_file(dest,lines=[],encoding='utf-8'):
 p = os.path.split(dest)[0]
 if not os.path.exists(p):
  os.makedirs(p)
 with io.open(file=dest,mode="a+",encoding=encoding) as fp:
  fp.writelines(lines)
if __name__ == '__main__':
  main()

python clean_csv.py --src=src.csv --dest=dest.csv --chunksize=50000 --cols --encoding=utf-8 --delimiter=,