从Python 3的列表中查找和提取模式字符串

Question

I have a data type list in Python 3 looks like this.

list1 = ['1128=9,9=639, 75=20140110,268=6,START,22=8,48=49798,83=63663,271=7,1020=7,5799=1,START,48=49798,83=63664,451=0,1003=2,5799=1','1128=9,9=6389, 75=20140119, START, 22=8,48=49798, 271=0.75,1020=7,5799=1,START,22=8,48=49798,83=63664,451=0,1020=10,5799=1,START,22=8,48=49798,271=63664,451=0,1020=10,5799=1']

The length of the list1 is 2.

I want to first extract all useful strings and omit all others.

I would like to keep everything with 52=, START, 75=, 271=, and 451=.

Then the desired output should be:

list2 = ['75=20140110, START,271=7,START,451=0','75=20140119, START, 271=0.75,START,451=0, START, 271=63664,451=0']

The last step is I would like to split the list and create a new list.

Within each element, I would like to paste the substring '75=.....' to the substrings after the word ' START'.

The desired output looks like.

list3 = ['75=20140110, START,271=7', '75=20140110,START,451=0','75=20140119, START, 271=0.75','75=20140119,START,451=0', '75=20140119,START, 271=63664,451=0']

Now, it is a list of 5 elements. We have 2 substring STARTs in list2, element 1, and 3 substring STARTs in list2, element 2.

I am new to Python, thank you so much for the help.

Answer 1

This should solve your first problem:

(You did not specify whether your use-case is sensitive to spaces so I ignored them)

list1 = [
    '1128=9,9=639, 75=20140110,268=6,START,22=8,48=49798,83=63663,271=7,1020=7,5799=1,START,48=49798,83=63664,451=0,1003=2,5799=1','1128=9,9=6389, 75=20140119, START, 22=8,48=49798, 271=0.75,1020=7,5799=1,START,22=8,48=49798,83=63664,451=0,1020=10,5799=1,START,22=8,48=49798,271=63664,451=0,1020=10,5799=1'
]

texts_to_keep = ['52=', 'START', '75=', '271=', '451=']

# Split the list on commas to work with the data easier
list1_split = [item.split(',') for item in list1]

# Create a new list of the same length as your old list1
list1_new = [[] for item in list1]
for items, list1_list in zip(list1_split, list1_new):
    # Grab each string in the sub list
    for item in items:
        # Now check if your substrings are in the original string
        for text_to_keep in texts_to_keep:
            # If it is, keep it
            if text_to_keep in item:
                list1_list.append(item)

final_list1 = [
    ','.join(sub_list) for sub_list in list1_new
]

Which gives the output:

[' 75=20140110,START,271=7,START,451=0', ' 75=20140119, START, 271=0.75,START,451=0,START,271=63664,451=0']

It should be possible to do this with a list comprehension for performance but it got very ugly so I went with the simple implementation above.

As per your second question, as far as I can tell, you're sometimes adding the substring '75=...' and sometimes not and I can't discern the pattern.

Answer 2

This should solve your first problem with help of list comprehension

 f = ['1128=9,9=639, 75=20140110,268=6,START,22=8,48=49798,83=63663,271=7,1020=7,5799=1,START,48=49798,83=63664,'
     '451=0,1003=2,5799=1',
     '1128=9,9=6389, 75=20140119, START, 22=8,48=49798, 271=0.75,1020=7,5799=1,START,22=8,48=49798,83=63664,'
     '451=0,1020=10,5799=1,START,22=8,48=49798,271=63664,451=0,1020=10,5799=1']

def convert(li):
    text = ['52=', 'START', '75=', '271=', '451=']
    return [", ".join([y for y in x.split(',') for z in text if z in y]) for x in li]

print(convert(f))
#output [' 75=20140110, START, 271=7, START, 451=0', ' 75=20140119,  START,  271=0.75, START, 451=0, START, 271=63664, 451=0']