Examples: Filtering¶

Example 1: Extract theta (STASH code 4) and pressure fields (STASH code 407) into a separate fieldsfile¶

import mule

ff = mule.FieldsFile.from_file("InputFile")

ff_out = ff.copy()

for field in ff.fields:
    if field.lbrel in (2,3) and field.lbuser4 in (4,407):
        ff_out.fields.append(field)

ff_out.to_file("OutputFile")

Note

Notice the check on lbrel - only fields with a valid release number will correctly support all named attributes, so this check must come before the check on lbuser4 to avoid errors.
In this case you could have instead used the hasattr function to look for the presence of lbuser4 directly, as an alternative.

Example 2: Remove all fields valid at 12Z¶

import mule

ff = mule.FieldsFile.from_file("InputFile")

for field in list(ff.fields):
    if field.lbrel in (2,3) and field.lbhrd == 12:
        ff.fields.remove(field)

ff.to_file("OutputFile")

Note

Notice the check on lbrel - only fields with a valid release number will correctly support all named attributes, so this check must come before the check on lbhrd to avoid errors.
In this case you could have instead used the hasattr function to look for the presence of lbhrd directly, as an alternative.

Example 3: Extract field numbers 3, 5 and 8¶

import mule

ff = mule.FieldsFile.from_file("InputFile")

ff_out = ff.copy()

# Remember Python uses 0-based indices for lists
ff_out.fields = [ff.fields[i-1] for i in [3,5,8]]

ff_out.to_file("OutputFile")

Example 4: Extract all 32 bit packed fields (LBPACK = 2) which have been unprocessed (LBPROC = 0)¶

import mule

ff = mule.FieldsFile.from_file("InputFile")

ff_out = ff.copy()

for field in ff.fields:
    if field.lbrel in (2,3) and field.lbpack == 2 and field.lbproc == 0:
        ff_out.fields.append(field)

ff_out.to_file("OutputFile")

Note

Notice the check on lbrel - only fields with a valid release number will correctly support all named attributes, so this check must come before the checks on lbpack and lbproc to avoid errors.

Example 5: Extract 38-level fields with STASH code 2, 3 and 4. The fields have to be 32 bit packed (LBPACK = 2) and unprocessed (LBPROC = 0) for STASH code 2 and 4¶

import mule

ff = mule.FieldsFile.from_file("InputFile")

ff_out = ff.copy()

for field in ff.fields:
    if field.lbrel in (2,3) and field.lblev == 38:
        if field.lbuser4 in (2,4) and field.lbpack == 2 and field.lbproc == 0:
            ff_out.fields.append(field)
        elif field.lbuser4 == 3:
            ff_out.fields.append(field)

ff_out.to_file("OutputFile")

Note

Notice the check on lbrel - only fields with a valid release number will correctly support all named attributes, so this check must come before the checks on lblev, lbuser4, etc. to avoid errors.