首先import os
然后调用os.system()函数
函数里面写命令,两端加上单引号’’

import os
filePre = '/home/zy/data/DEPGRAPH_yang_python3/detection_file/traceSmall_walkPre.csv'
fileSub = '/home/zy/data/DEPGRAPH_yang_python3/detection_file/traceSmall_walkSub.csv'
write_file = '/home/zy/data/DEPGRAPH_yang_python3/detection_file/traceSmall_walk.csv'
os.system('cat ' + filePre + " >> " + write_file +' ; '+'cat ' + fileSub + " >> " + write_file)

为了保证system执行多条命令可以成功,多条命令需要在同一个子进程中运行
;可以连接两个命令。
一个直观的例子:

import os
os.system('cd /usr/local && mkdir aaa.txt')
# 或者
os.system('cd /usr/local ; mkdir aaa.txt')