用天鹅绒组装dna；它运行天鹅绒，但不重组天鹅绒

Question

我有上面的代码来运行velvet。我可以毫无问题地运行velveth，但它无法识别velvetg的参数。我已经检查了文件，我看不出有什么不同。当程序到达velveteg时，我得到以下消息：[0.000000]未知选项：-ins\u length 500.

import glob, sys, os, subprocess

def velvet_project():
    print 'starting_velvet'
    #'this is the directory where I copied the two test files. H*, I realised this is a subdirectory *.gastq.gz, to process all the files with that extention' 
    folders = glob.glob('/home/my_name/fastqs_test/H*')
    #print folders
    for folder in folders:
        print folder
        #looking for fastqs in each folder
        fastqs=glob.glob(folder + '/*.fastq.gz')
        #print fastqs
        strain_id = os.path.basename(folder)
        output= '/home/my_name/velvet_results/' + strain_id + '_velvet'
        if os.path.exists(output):
            print 'velevet folder already exist'
        else:
            os.makedirs(output)
        #cmd is a command line within the programme#
        cmd=['velveth', output, '59', '-fastq.gz','shortPaired',fastqs[0],fastqs[1]]
        #print cmd
        my_file=subprocess.Popen(cmd)#I got this from the documentation.
        my_file.wait()
        print 'velveth has finished'
        cmd_2=['velvetg', output, '-ins_length 500', '-exp_cov auto', '-scaffoding no']
        print cmd_2
        my_file_2=subprocess.Popen(cmd_2)
        my_file_2.wait()
        print "velvet has finished :)"

print 'start'
velvet_project()