[英]How to parse a value next to a specific substring in Python
我有一个日志文件,其中包含格式如下所示的行。 我想解析子字符串element=(string)
、 time=(guint64)
和ts=(guint64)
旁边的值,并将它们保存到一个列表中,该列表将包含每行的单独列表:
0:00:00.336212023 62327 0x55f5ca5174a0 TRACE GST_TRACER :0:: element-latency, element-id=(string)0x55f5ca532a60, element=(string)rawvideoparse0, src=(string)src, time=(guint64)852315, ts=(guint64)336203035;
0:00:00.336866520 62327 0x55f5ca5176d0 TRACE GST_TRACER :0:: element-latency, element-id=(string)0x55f5ca53f860, element=(string)nvh264enc0, src=(string)src, time=(guint64)6403181, ts=(guint64)336845676;
最终的 output 将如下所示: [['rawvideoparse0', 852315, 336203035], ['nvh264enc0', 6403181, 336845676]]
。
我可能应该使用 Python 的字符串拆分或分区方法来获取每一行中的相关部分,但我无法提出一个可以概括为我正在搜索的值的简短解决方案。 我也不知道如何处理 values element
和time
以逗号结尾而ts
以分号结尾的事实(没有为这两种情况编写单独的条件)。 如何使用 Python 中的字符串操作方法来实现这一点?
这是使用一系列拆分命令的可能解决方案:
output = []
with open("log.txt") as f:
for line in f:
values = []
line = line.split("element=(string)", 1)[1]
values.append(line.split(",", 1)[0])
line = line.split("time=(guint64)", 1)[1]
values.append(int(line.split(",", 1)[0]))
line = line.split("ts=(guint64)", 1)[1]
values.append(int(line.split(";", 1)[0]))
output.append(values)
正则表达式是为此而设计的:
lines = """
0:00:00.336212023 62327 0x55f5ca5174a0 TRACE GST_TRACER :0:: element-latency, element-id=(string)0x55f5ca532a60, element=(string)rawvideoparse0, src=(string)src, time=(guint64)852315, ts=(guint64)336203035;
0:00:00.336866520 62327 0x55f5ca5176d0 TRACE GST_TRACER :0:: element-latency, element-id=(string)0x55f5ca53f860, element=(string)nvh264enc0, src=(string)src, time=(guint64)6403181, ts=(guint64)336845676;
"""
import re
pattern = re.compile(".*element-id=\\(string\\)(?P<elt_id>.*), element=\\(string\\)(?P<elt>.*), src=\\(string\\)(?P<src>.*), time=\\(guint64\\)(?P<time>.*), ts=\\(guint64\\)(?P<ts>.*);")
for l in lines.splitlines():
match = pattern.match(l)
if match:
results = match.groupdict()
print(results)
产生以下字典(请注意,捕获的组已在上面的正则表达式中使用(?P<name>...)
,这就是我们有这些名称的原因):
{'elt_id': '0x55f5ca532a60', 'elt': 'rawvideoparse0', 'src': 'src', 'time': '852315', 'ts': '336203035'}
{'elt_id': '0x55f5ca53f860', 'elt': 'nvh264enc0', 'src': 'src', 'time': '6403181', 'ts': '336845676'}
您可以使这个正则表达式模式更加通用,因为所有元素共享一个共同的结构<name>=(<type>)<value>
:
pattern2 = re.compile("(?P<name>[^,;\s]*)=\\((?P<type>[^,;]*)\\)(?P<value>[^,;]*)")
for l in lines.splitlines():
all_interesting_items = pattern2.findall(l)
print(all_interesting_items)
它产生:
[]
[('element-id', 'string', '0x55f5ca532a60'), ('element', 'string', 'rawvideoparse0'), ('src', 'string', 'src'), ('time', 'guint64', '852315'), ('ts', 'guint64', '336203035')]
[('element-id', 'string', '0x55f5ca53f860'), ('element', 'string', 'nvh264enc0'), ('src', 'string', 'src'), ('time', 'guint64', '6403181'), ('ts', 'guint64', '336845676')]
请注意,在所有情况下, https://regex101.com/都是您调试正则表达式的朋友:)
这不是最快的解决方案,但这可能是我为了可读性而编写它的方式。
# create empty list for output
list_final_output = []
# filter substrings
list_filter = ['element=(string)', 'time=(guint64)', 'ts=(guint64)']
# open the log file and read in the lines as a list of strings
with open('so_58272709.log', 'r') as f_log:
string_example = f_log.read().splitlines()
print(f'string_example: \n{string_example}\n')
# loop through each line in the list of strings
for each_line in string_example:
# split each line by comma
list_split_line = each_line.split(',')
# loop through each filter substring, include filter
filter_string = [x for x in list_split_line if (list_filter[0] in x
or list_filter[1] in x
or list_filter[2] in x
)]
# remove the substring
filter_string = [x.replace(list_filter[0], '') for x in filter_string]
filter_string = [x.replace(list_filter[1], '') for x in filter_string]
filter_string = [x.replace(list_filter[2], '') for x in filter_string]
# store results of each for-loop
list_final_output.append(filter_string)
# print final output
print(f'list_final_output: \n{list_final_output}\n')
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