使用Python瞬间生成超大文件

import time
def creatfilesize(n):
local_time = time.strftime("%Y%m%d%H%M%S",time.localtime())
file_name = "E:\\"+str(local_time)+".txt"
bigFile= open(file_name, 'w')
bigFile.seek(1024*1024*1024*n)
bigFile.write('test')
#bigFile.write("test")
bigFile.close()
print "ALL down !"

if __name__ == '__main__':
n = input("input:")
creatfilesize(n)