Python正则表达式模式匹配

Question

I have a list in the following format:

data =['| test_data_14865428_0              |', '| test_data_1486612450_0              |', '| test_template                  |', '|id_1475020800_0              |']

I want to fetch all the list elements of the format test_data_* into a new list (tables). The list tables should store the name in the format test_data_*

My try:

import re
tables = []
pattern = re.compile("| test_data\S")

for i in range(0, len(data)):
    if pattern.match(data[i]):
        tables.append(data[i])

print(list_of_tables)

Answer 1

Since all of your data includes the substring test_data_ you could filter for that static phrase without requiring a regex:

data = filter(lambda v: 'test_data_' in v, data)

If you then want to filter out the space and pipe separators you could use translate to remove the unwanted characters:

data = map(lambda v: v.translate(None, " |"), data)

Of course the expressions could be combined into a compound expression.

---

One problem with the regex in the original code above is that the | needs to be escaped so it will be treated literally. Currently it is treated as an alternate operator.

Though perhaps not the most elegant implementation, the following is one option:

import re
pattern = re.compile("\| *(test_data_[\d_]+)")
def search(val):
    found = pattern.match(val)
    return found and found.group(1)
print(filter(lambda f: f, map(search, data)))

The filter with the identity map just removes records that had no match.

Answer 2

Use filter to select the values that contain "test_data_", then map a function across those values to clean up the strings. No regex required.

import operator

td = map(lambda s: s[2:].split(' ', 1)[0], 
         filter(operator.methodcaller('startswith', '| test_data_'),
                data))
print(list(td))