file.py

counta = 0
countb = 0
countc = 0
with open( "a.txt", 'a') as a:
  with open( "b.txt", 'a') as b:
    with open( "c.txt", 'a') as c:
      # Iterate over readlines from myFile.xml and parse data 
      if ( counta == 300000 ): 
        with open( "a1.txt" , 'a') as a1:
          a1.write()...
      if ( countb ==   ):
      if ( countc ==  ) : 
      
      # if the if blocks accessed above then continue without going below to write in a b c
      ............
      a.write()
      b.write()
      c.write()
      counta += 1 
      countb += 1
      countc += 1