Question

我们说我有一个这样的字符串：

Benchmark\r\n\tRunning for engine innodb\r\n\tAverage number of seconds to run all queries: 0.374 seconds\r\n\tMinimum number of seconds to run all queries: 0.374 seconds\r\n\tMaximum number of seconds to run all queries: 0.374 seconds\r\n\tNumber of clients running queries: 1\r\n\tAverage number of queries per client: 2

如果我只对值后跟“平均运行所有查询的秒数”感兴趣：＆＃39;，我该如何获取？

Answer 1

这个问题的一个难题是使用正则表达式，因为正则表达式是处理模式匹配的一般方法。

例如，您可以使用以下代码在此处解决您的问题：

import re
mystring = 'Your input'

float_pattern = '(\d*\.\d*)'
prefix = 'Average number of seconds to run all queries: '
postfix = ' seconds'
all_time = re.findall(prefix+float_pattern+postfix,mystring)
all_time_t = map(lambda x:float(x),all_time)
average_time = sum(all_time_t)/len(all_time_t)

阅读正则表达式文档以获取更多信息：https://docs.python.org/2/library/re.html

Answer 2

您可以split()字符串，并将值添加到字典中。然后，您可以根据需要访问所有值。

a = Benchmark\r\n\tRunning for engine innodb\r\n\tAverage number of seconds to run all queries: 0.374 seconds\r\n\tMinimum number of seconds to run all queries: 0.374 seconds\r\n\tMaximum number of seconds to run all queries: 0.374 seconds\r\n\tNumber of clients running queries: 1\r\n\tAverage number of queries per client: 2
lst = a.split("k\r\n\")
d = {}
for i in z[2:]:    
    k,v = i.split(":")
    d[k] = v

或者

d = dict((k,v) for k,v in (i.split(':') for i in a.split("\r\n\t")[2:]))

现在，您可以通过执行

来访问所有值

d["Average number of seconds to run all queries"]
>>>' 0.374 seconds'

Answer 3

我的解决方案非常特定于您提供的数据，并且不会很好地概括，但在此您是：

import re

teststring="Benchmark\r\n\tRunning for engine innodb\r\n\tAverage number of seconds to run all queries: 0.374 seconds\r\n\tMinimum number of seconds to run all queries: 0.374 seconds\r\n\tMaximum number of seconds to run all queries: 0.374 seconds\r\n\tNumber of clients running queries: 1\r\n\tAverage number of queries per client: 2"
prog = re.compile(".*Average number of seconds to run all queries: (\d+\.\d+) seconds.*", re.DOTALL)
result = prog.match(teststring)
print result.group(1)

输出：

macbook:Downloads joeyoung$ python regextest.py 
0.374

Python：如何从字符串中获取一个数字后跟一个特定的关键字

3 个答案: