如何从文件的特定行中提取特定部分？

Question

I have a.yml file that I need to extract a specific part from specific lines.

This is what part of the file looks like (The file is 1200+ lines, but the structure is similar all throughout):

training:
trainings:
  - workout: Rec 016
    performed_at: 2020-06-25 09:04:16.295000076 Z
    star: false
    time: '00:04:00'
  - workout: Hanging knee raises endurance 10
    performed_at: 2020-06-25 08:59:11.871999979 Z
    star: true
    time: '00:00:28'
    repetitions: 10
  - workout: Str 700
    performed_at: 2020-06-25 08:57:51.039999961 Z
    star: true
    time: '00:15:30'
  - workout: Supermans technical 30
    performed_at: 2020-06-25 08:38:45.894000053 Z
    star: true
    time: '00:01:02'
  - workout: Toe touch crunches technical 20
    performed_at: 2020-06-25 08:37:05.439000129 Z
    star: true
    time: '00:00:54'
  - workout: Pre 028
    performed_at: 2020-06-25 08:35:33.243999958 Z
    star: false
    time: '00:06:30'
  - workout: Rec 001
    performed_at: 2020-06-22 22:51:38.947000026 Z
    star: false
    time: '00:05:01'
  - workout: Burpees standard 10
    performed_at: 2020-06-22 22:46:00.807000160 Z
    star: true
    time: '00:00:38'

Extra Info: With the following code:

df = pd.read_csv(r'text_data.yml')

with pd.option_context("display.max_rows", None, "display.max_columns", None):
    print(df)

This is what the file transforms into:

                                                    ---
0                                             training:
1                                            trainings:
2                                    - workout: Rec 016
3         performed_at: 2020-06-25 09:04:16.295000076 Z
4                                           star: false
5                                      time: '00:04:00'
6           - workout: Hanging knee raises endurance 10
7         performed_at: 2020-06-25 08:59:11.871999979 Z
8                                            star: true
9                                      time: '00:00:28'
10                                      repetitions: 10
11                                   - workout: Str 700
12        performed_at: 2020-06-25 08:57:51.039999961 Z
13                                           star: true
14                                     time: '00:15:30'
15                    - workout: Supermans technical 30
16        performed_at: 2020-06-25 08:38:45.894000053 Z
17                                           star: true
18                                     time: '00:01:02'
19           - workout: Toe touch crunches technical 20
20        performed_at: 2020-06-25 08:37:05.439000129 Z
21                                           star: true
22                                     time: '00:00:54'
23                                   - workout: Pre 028
24        performed_at: 2020-06-25 08:35:33.243999958 Z
25                                          star: false
26                                     time: '00:06:30'
27                                   - workout: Rec 001
28        performed_at: 2020-06-22 22:51:38.947000026 Z
29                                          star: false
30                                     time: '00:05:01'

What I am trying to do is extract the dates (Only the dates, nothing else) that are in the lines that start with "performed_at:" and put them into a list/DataFrame.

How would I go about doing this in the most efficient way possible through Pandas?

Answer 1

For the solution, please read the comments made under the question. Thanks to @dm2.