Python：如何解析 "return" 字符串
Python: How to parse a "return" string
我正在编写一个通过导入使用现有框架的小工具。
我使用的部分是：
def exec_command(self, command, timeout=60, mode=cli.CLIMode.UNDEF,
output_expected=None, error_expected=False, prompt=None):
"""Executes the given command.
This method handles detecting simple boolean conditions such as
the presence of output or errors.
:param command: command to execute, newline appended automatically
:param timeout: maximum time, in seconds, to wait for the command to
finish. 0 to wait forever.
:param mode: mode to enter before running the command. The default
is :func:`default_mode`. To skip this step and execute directly
in the cli's current mode, explicitly set this parameter to None.
:param output_expected: If not None, indicates whether output is
expected (True) or no output is expected (False).
If the opposite occurs, raise UnexpectedOutput. Default is None.
:type output_expected: bool or None
:param error_expected: If true, cli error output (with a leading '%')
is expected and will be returned as regular output instead of
raising a CLIError. Default is False, and error_expected always
overrides output_expected.
:type error_expected: bool
:param prompt: Prompt regex for matching unusual prompts. This should
almost never be used as the ``mode`` parameter automatically
handles all typical cases. This parameter is for unusual
situations like the install config wizard.
:return: output of the command, minus the command itself.
:raises CmdlineTimeout: on timeout
:raises CLIError: if the output matches the cli's error format, and
error output was not expected.
:raises UnexpectedOutput: if output occurs when no output was
expected, or no output occurs when output was expected
"""
if output_expected is not None and type(output_expected) is not bool:
raise TypeError("exec_command: output_expected requires a boolean "
"value or None")
if mode is cli.CLIMode.UNDEF:
mode = self.default_mode
if mode is not None:
self.enter_mode(mode)
self._log.debug('Executing cmd "%s"' % command)
if prompt is None:
prompt = self._prompt
(output, match_res) = self._send_line_and_wait(command,
prompt,
timeout=timeout)
# CLI adds on escape chars and such sometimes and the result is that
# some part of the command that was entered shows up as an extra
# initial line of output. Strip off that initial line.
output = '\n'.join(output.splitlines()[1:])
if output and (re.match(self.CLI_ERROR_PROMPT, output)):
if error_expected:
# Skip output_expected processing entirely.
return output
else:
try:
mode = self.current_cli_mode()
except exceptions.UnknownCLIMode:
mode = '<unrecognized>'
raise exceptions.CLIError(command, output=output, mode=mode)
if ((output_expected is not None) and (bool(output) !=
bool(output_expected))):
raise exceptions.UnexpectedOutput(command=command,
output=output,
expected_output=output_expected)
return output
我在脚本中使用：
print sh.cli.exec_command(command, mode="enable")
这很好用。该工具正在登录设备，执行命令。根据框架，它的 "return" 是“:return：命令的输出，减去命令本身。”这也可以正常工作，当执行命令时，我得到：
Generated dump sysdump-csh-20150320-140445.tgz
完美！
对于下一步，我需要创建转储的名称，即没有 "Generated dump " 文本的 return 字符串。
现在我正在努力将其解析为一个新变量，例如下载生成的转储并在之后删除它，等等
s = "Generated dump sysdump-csh-20150320-140445.tgz"
print s.split()[-1]
产量
"sysdump-csh-20150320-140445.tgz"
这只是通过空格分割来解析。每个解析决定都取决于一些假设。这取决于假设您想要的文件名是连续的（没有内部空格），以及空白拆分列表中的最后一项。
Martijn Pieters 先于我改进了这个公式：
s.split(None, 2)[-1]
甚至更好：
s.strip().split(None, 2)[-1]
这是最好的，因为它也不假定文件名是连续的。 .strip() 还删除了没有尾随空格的假设。
请记住，无论您选择哪种简单的解析策略，它始终取决于假设。例如，即使在这里改进了公式，我们仍然假设文件名是行中的最后一项。如果生成此行的程序更新为 "Generated dump sysdump-csh-20150320-140445.tgz on March 20, 2015." 说，我们将不得不用另一种方式来欺骗它。
您可以只使用字符串切片来获取没有 Generated dump 部分的部分：
dump_name = return_value[15:]
其中 15 是文本的长度 Generated dump 加上 space.
其他选项包括在白色上拆分space；但要注意只拆分前两个 spaces:
dump_name = return_value.split(None, 2)[-1]
这在任意白色space上拆分2次；单词之间有 1 个还是 10 个 space 并不重要。或制表符、换行符、不间断的 spaces 等，之后选择结果列表的最后一个元素。
我正在编写一个通过导入使用现有框架的小工具。
我使用的部分是：
def exec_command(self, command, timeout=60, mode=cli.CLIMode.UNDEF,
output_expected=None, error_expected=False, prompt=None):
"""Executes the given command.
This method handles detecting simple boolean conditions such as
the presence of output or errors.
:param command: command to execute, newline appended automatically
:param timeout: maximum time, in seconds, to wait for the command to
finish. 0 to wait forever.
:param mode: mode to enter before running the command. The default
is :func:`default_mode`. To skip this step and execute directly
in the cli's current mode, explicitly set this parameter to None.
:param output_expected: If not None, indicates whether output is
expected (True) or no output is expected (False).
If the opposite occurs, raise UnexpectedOutput. Default is None.
:type output_expected: bool or None
:param error_expected: If true, cli error output (with a leading '%')
is expected and will be returned as regular output instead of
raising a CLIError. Default is False, and error_expected always
overrides output_expected.
:type error_expected: bool
:param prompt: Prompt regex for matching unusual prompts. This should
almost never be used as the ``mode`` parameter automatically
handles all typical cases. This parameter is for unusual
situations like the install config wizard.
:return: output of the command, minus the command itself.
:raises CmdlineTimeout: on timeout
:raises CLIError: if the output matches the cli's error format, and
error output was not expected.
:raises UnexpectedOutput: if output occurs when no output was
expected, or no output occurs when output was expected
"""
if output_expected is not None and type(output_expected) is not bool:
raise TypeError("exec_command: output_expected requires a boolean "
"value or None")
if mode is cli.CLIMode.UNDEF:
mode = self.default_mode
if mode is not None:
self.enter_mode(mode)
self._log.debug('Executing cmd "%s"' % command)
if prompt is None:
prompt = self._prompt
(output, match_res) = self._send_line_and_wait(command,
prompt,
timeout=timeout)
# CLI adds on escape chars and such sometimes and the result is that
# some part of the command that was entered shows up as an extra
# initial line of output. Strip off that initial line.
output = '\n'.join(output.splitlines()[1:])
if output and (re.match(self.CLI_ERROR_PROMPT, output)):
if error_expected:
# Skip output_expected processing entirely.
return output
else:
try:
mode = self.current_cli_mode()
except exceptions.UnknownCLIMode:
mode = '<unrecognized>'
raise exceptions.CLIError(command, output=output, mode=mode)
if ((output_expected is not None) and (bool(output) !=
bool(output_expected))):
raise exceptions.UnexpectedOutput(command=command,
output=output,
expected_output=output_expected)
return output
我在脚本中使用：
print sh.cli.exec_command(command, mode="enable")
这很好用。该工具正在登录设备，执行命令。根据框架，它的 "return" 是“:return：命令的输出，减去命令本身。”这也可以正常工作，当执行命令时，我得到：
Generated dump sysdump-csh-20150320-140445.tgz
完美！ 对于下一步，我需要创建转储的名称，即没有 "Generated dump " 文本的 return 字符串。
现在我正在努力将其解析为一个新变量，例如下载生成的转储并在之后删除它，等等
s = "Generated dump sysdump-csh-20150320-140445.tgz"
print s.split()[-1]
产量
"sysdump-csh-20150320-140445.tgz"
这只是通过空格分割来解析。每个解析决定都取决于一些假设。这取决于假设您想要的文件名是连续的（没有内部空格），以及空白拆分列表中的最后一项。
Martijn Pieters 先于我改进了这个公式：
s.split(None, 2)[-1]
甚至更好：
s.strip().split(None, 2)[-1]
这是最好的，因为它也不假定文件名是连续的。 .strip() 还删除了没有尾随空格的假设。
请记住，无论您选择哪种简单的解析策略，它始终取决于假设。例如，即使在这里改进了公式，我们仍然假设文件名是行中的最后一项。如果生成此行的程序更新为 "Generated dump sysdump-csh-20150320-140445.tgz on March 20, 2015." 说，我们将不得不用另一种方式来欺骗它。
您可以只使用字符串切片来获取没有 Generated dump 部分的部分：
dump_name = return_value[15:]
其中 15 是文本的长度 Generated dump 加上 space.
其他选项包括在白色上拆分space；但要注意只拆分前两个 spaces:
dump_name = return_value.split(None, 2)[-1]
这在任意白色space上拆分2次；单词之间有 1 个还是 10 个 space 并不重要。或制表符、换行符、不间断的 spaces 等，之后选择结果列表的最后一个元素。