如何从包含相同单词的行数的文件中仅一次提取给定单词的行

Question

I have data file which contains data for a month. File format is like:

VAAU Observations at 00Z 02 Aug 2017

-------------------------------------------------------------------------------------------
   PRES   HGHT   TEMP   DWPT   FRPT   RELH   RELI   MIXR   DRCT   SKNT   THTA   THTE   THTV
    hPa     m      C      C      C      %      %    g/kg    deg   knot     K      K      K
-------------------------------------------------------------------------------------------
 1000.0     66
  942.0    579   22.6   20.3   20.3     87     87  16.20    270      4  300.8  348.6  303.8
  925.0    747   21.6   19.9   19.9     90     90  16.09    265     10  301.4  348.9  304.3
  850.0   1481   18.8   17.1   17.1     90     90  14.65    275     19  305.8  350.0  308.5
  812.0   1873   17.3   14.1   14.1     82     82  12.60    275     22  308.2  346.6  310.6
...................
Station information and sounding indices
                         Station identifier: VAAU
                             Station number: 43014
                           Observation time: 170801/0000
                           Station latitude: 19.85
                          Station longitude: 75.40
                          Station elevation: 579.0
                            Showalter index: 0.92
                               Lifted index: 0.99
    LIFT computed using virtual temperature: 0.46
                                SWEAT index: 255.81
                                    K index: 34.70
                         Cross totals index: 19.70
                      Vertical totals index: 20.10
                        Totals totals index: 39.80
      Convective Available Potential Energy: 5.98
             CAPE using virtual temperature: 9.37
                      Convective Inhibition: -81.35
             CINS using virtual temperature: -69.07
                           Equilibrum Level: 617.53
 Equilibrum Level using virtual temperature: 523.66
                   Level of Free Convection: 662.87
             LFCT using virtual temperature: 669.25
                     Bulk Richardson Number: 4.12
          Bulk Richardson Number using CAPV: 6.44
  Temp [K] of the Lifted Condensation Level: 292.45
Pres [hPa] of the Lifted Condensation Level: 894.64
     Mean mixed layer potential temperature: 301.92
              Mean mixed layer mixing ratio: 16.03
              1000 hPa to 500 hPa thickness: 5818.00
Precipitable water [mm] for entire sounding: 51.19

The same thing will repeat for every day for a month. I want to extract Station identifier, Station number, Station latitude & Station longitude only once from that file.

I tried with python script but didn't get desired output. Even I tried with grep as well:

grep -E "Station number|Station latitude|Station longitude|Station identifier" wrkk_2017.out


for line in open('vaau_2017.out'):
    rec = line.strip()
    words = ["Station identifier:", "Station number:", "Station latitude:", "Station longitude"]
    for rec in words:
        if rec in line:
            print (line)
            break

I am expecting only Station identifier: ..., Station number:...., Station latitude:......, Station longitude:.... Only once but I'm getting it number of times as it is there in that file.

Answer 1

You could add a boolean array in which you save if a word was already found:

still_left = [True] * len(words)

for line in open('vaau_2017.out'):
    for i, w in enumerate(words):
        if w in line and still_left[i]:
            print(line)
            still_left[i] = False
    if sum(still_left)==0:
        break

Example:

s = '''id: 1
num: 2
lat: 3
lon: 4
id: 1
num: 2
lat: 3
lon: 4'''

words = ['id', 'num', 'lat', 'lon']
still_left = [True] * len(words)

for line in s.splitlines():              # for line in open('vaau_2017.out'):
    for i, w in enumerate(words):
        if w in line and still_left[i]:
            print(line)
            still_left[i] = False
# id: 1
# num: 2
# lat: 3
# lon: 4

and if you want to break reading the file as soon as all words are found, you can add

    if sum(still_left)==0:
        break

at the for line... level behind the inner for i, w... loop.

Answer 2

You can do with regex -

a = 'Station information and sounding indices Station identifier: VAAU Station number: 43014 Observation time: 170801/0000 Station latitude: 19.85 Station longitude: 75.40 Station elevation: 579.0 Showalter index: 0.92 Lifted index: 0.99 LIFT computed using virtual temperature: 0.46 SWEAT index: 255.81 K index: 34.70 Cross totals index: 19.70 Vertical totals index: 20.10'

station_identifier = re.search('Station identifier: ([A-Z]+)',a).group(1)
print station_identifier #VAAU

station_number = re.search('Station number: ([+-]?(\d+(\.\d*)?|\.\d+)([eE][+-]?\d+)?)',a).group(1)
print station_number #43014

station_latitude = re.search('Station latitude: ([+-]?(\d+(\.\d*)?|\.\d+)([eE][+-]?\d+)?)',a).group(1)
print station_latitude #19.85

station_longitude = re.search('Station longitude: ([+-]?(\d+(\.\d*)?|\.\d+)([eE][+-]?\d+)?)',a).group(1)
print station_longitude #75.40

Learning Path:

https://www.programiz.com/python-programming/regex

EDIT:

Solution to your question -

filename = "vaau_2017.out"
with open(filename) as f:
    for line in f.readlines():

        if 'Station identifier' in line:
            station_identifier = re.search('Station identifier: ([\sA-Z]+)',line).group(1)
            print station_identifier #VAAU

        if 'Station number' in line:
            station_number = re.search('Station number: ([+-]?(\d+(\.\d*)?|\.\d+)([eE][+-]?\d+)?)',line).group(1)
            print station_number #43014

        if 'Station latitude' in line:
            station_latitude = re.search('Station latitude: ([+-]?(\d+(\.\d*)?|\.\d+)([eE][+-]?\d+)?)',line).group(1)
            print station_latitude #19.85

        if 'Station longitude' in line:
            station_longitude = re.search('Station longitude: ([+-]?(\d+(\.\d*)?|\.\d+)([eE][+-]?\d+)?)',line).group(1)
            print station_longitude #75.40