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

Question

我正在處理以下一段Python代碼。代碼非常簡單，pexpect將echo testcase發送到終端，然後監視終端以查看testcase的後續出現，然後通過設置bool_value=True（假設它看到預期的輸出）來驗證它是否看到了回顯。

#!/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() 

我有什麼期望看到的是，第一個測試用例後，bool_value將打印True。在這種情況下，它只會在添加設置爲bool_value = not testcase.expect('testcase')的奇怪黑客之後（將其設置爲expect（）返回的逆函數）。

在第二個測試案例中，testcase.expect()未看到預期值someothervalue，所以我預計它會返回false。相反，它會返回一個異常：

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 

我真的不確定如何根據文檔告訴我的情況來糾正此問題。按this previous implementation添加testcase.expect(pexpect.EOF())返回相同的錯誤。

如何正確實現此功能？

Answer 1

事實證明，當系統不在輸出東西pexpect正在尋找時，它會觸發pexpect.EOF而不觸發任何形式的動作。因爲我沒有告訴它在遇到EOF時沒有看到它期望的任何其他字符串時該做什麼，而是返回異常。

這裏是我的代碼更正和測試用例。

#!/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()