title: openpyxl not able to open more than 65k rows
body: <p>i have a xlsx file which has 500,000 rows.I want to copy it into a csv file, but I am only able to copy 65k rows and then the program ends.here is my code i am using for copying data from xlsx file to csv file.amd it is taking too much time to even print 65k lines.</p>
  
  <pre><code>import openpyxl
  import csv
  import time
  import collections
  
  def csv_from_excel() :
      t1=(time.time())*1000
      workbook = openpyxl.load_workbook(filename = '5lac_xlsx.xlsx',optimized_read = True, use_iterators = True)
      sh=workbook.get_sheet_by_name('Sheet1')
      your_csv_file = open('your_csv_file.csv','wb')
      wr = csv.writer(your_csv_file,quoting=csv.QUOTE_ALL)
      t2=(time.time())*1000
      print (t2-t1)
      fp = open('your_csv_file.csv', 'wb')
      a = csv.writer(fp, delimiter=',')
  
      m1=(time.time())*1000
      count=0
  
      for row_t in sh.iter_rows():
          for cell in row_t :
              try :
                  count=count+1
                  wr.writerow([cell[3]])  
                  #wr.writerow('\n')
              except :
                  print "error"
  
      print "count"
      print count
  
      your_csv_file.close()
  
      m2=(time.time())*1000
      print (m2-m1)
  
  csv_from_excel()
  </code></pre>