Python pexpect：var.expect（'string'）'string'未找到时不返回期望值

Question

我正在处理以下一段Python代码。代码非常简单，pexpect将echo testcase发送到终端，然后监视终端以查看testcase的后续出现，然后通过设置bool_value=True（假设它看到预期的输出）来验证它是否看到了回显。

#!/usr/bin/python 
import pexpect 

print('Testing case where pexpect finds the expected value: ') 
testcase = pexpect.spawn('echo testcase') 
bool_value = not testcase.expect('testcase') 
print bool_value 
testcase.close() 

print('Testing case where pexpect does not find the expected value: ') 
testcase = pexpect.spawn('echo testcase') 
bool_value = not testcase.expect('someothervalue') 
print bool_value 
testcase.close() 

我有什么期望看到的是，第一个测试用例后，bool_value将打印True。在这种情况下，它只会在添加设置为bool_value = not testcase.expect('testcase')的奇怪黑客之后（将其设置为expect（）返回的逆函数）。

在第二个测试案例中，testcase.expect()未看到预期值someothervalue，所以我预计它会返回false。相反，它会返回一个异常：

Traceback (most recent call last): 
    File "./echotest.py", line 12, in <module> 
    bool_value = not testcase.expect('someothervalue') 
    File "/usr/lib/python2.7/dist-packages/pexpect/__init__.py", line 1418, in expect 
    timeout, searchwindowsize) 
    File "/usr/lib/python2.7/dist-packages/pexpect/__init__.py", line 1433, in expect_list 
    timeout, searchwindowsize) 
    File "/usr/lib/python2.7/dist-packages/pexpect/__init__.py", line 1521, in expect_loop 
    raise EOF(str(err) + '\n' + str(self)) 
pexpect.EOF: End Of File (EOF). Exception style platform. 
<pexpect.spawn object at 0x7f7667a9db10> 
version: 3.1 
command: /bin/echo 
args: ['/bin/echo', 'testcase'] 
searcher: <pexpect.searcher_re object at 0x7f7667a9d790> 
buffer (last 100 chars): '' 
before (last 100 chars): 'testcase\r\n' 
after: <class 'pexpect.EOF'> 
match: None 
match_index: None 
exitstatus: 0 
flag_eof: True 
pid: 4619 
child_fd: 3 
closed: False 
timeout: 30 
delimiter: <class 'pexpect.EOF'> 
logfile: None 
logfile_read: None 
logfile_send: None 
maxread: 2000 
ignorecase: False 
searchwindowsize: None 
delaybeforesend: 0.05 
delayafterclose: 0.1 
delayafterterminate: 0.1 

我真的不确定如何根据文档告诉我的情况来纠正此问题。按this previous implementation添加testcase.expect(pexpect.EOF())返回相同的错误。

如何正确实现此功能？

Answer 1

事实证明，当系统不在输出东西pexpect正在寻找时，它会触发pexpect.EOF而不触发任何形式的动作。因为我没有告诉它在遇到EOF时没有看到它期望的任何其他字符串时该做什么，而是返回异常。

这里是我的代码更正和测试用例。

#!/usr/bin/python 
import pexpect 

""" 
Test for some known good value. 
""" 
print('Testing case where pexpect finds the expected value: ') 
testcase = pexpect.spawn('echo testcase') 
bool_value = testcase.expect([pexpect.EOF,'testcase','badcase']) 
if bool_value == 0: 
    print('Unknown value presented to script.') 
elif bool_value == 1: 
    print('Success.') 
elif bool_value == 2: 
    print('Failed.') 
print bool_value 
testcase.close() 

""" 
Test for some known bad response 
""" 
print('Testing case where pexpect finds an expected bad value: ') 
testcase = pexpect.spawn('echo badcase') 
bool_value = testcase.expect([pexpect.EOF,'testcase','badcase']) 
if bool_value == 0: 
    print('Unknown value presented to script.') 
elif bool_value == 1: 
    print('Success.') 
elif bool_value == 2: 
    print('Failed.') 
print bool_value 
testcase.close() 

""" 
If it gets no expected response at all, it will reach EOF. We have to define 
some behavior for that case. 
""" 
print('Testing case where pexpect does not find any expected value: ') 
testcase = pexpect.spawn('echo unknown') 
bool_value = testcase.expect([pexpect.EOF,'testcase','badcase']) 
if bool_value == 0: 
    print('Unknown value presented to script.') 
elif bool_value == 1: 
    print('Success.') 
elif bool_value == 2: 
    print('Failed.') 
print bool_value 
testcase.close()