FieldPyculator code execute error when using Advanced Python field calculator in QGIS

Question

In QGIS I have the following script that evaluates the results in each feature then gives it a value. Some of the values are NULL, which is fine, but how do I get the Advanced Python field calculator to deal with it?

I get the following error that I think is due to my NULL syntax:

FieldPyculator code execute error. Global code block can't be executed! SyntaxError invalid syntax (, line 4) Execution failed after 0.02 seconds

def getValue(distance, SPECIES_NM, F_SEN_ZN_1):
    if distance == None:
        value = 0.50
    elif SPECIES_NM is not None AND F_SEN_ZN_1 == 'No' AND distance <= 100: 
        value = 0.75 
    elif SPECIES_NM is not None AND F_SEN_ZN_1 is None AND distance <= 100:
        value = 0.50
    elif SPECIES_NM is not None AND F_SEN_ZN_1 = 'No' AND distance <= 100:
        value = 0.50
    elif SPECIES_NM is None AND F_SEN_ZN_1 = 'Yes' AND distance <= 100:
        value = 1.0
    elif SPECIES_NM is not None AND F_SEN_ZN_1 = 'Yes' AND distance <= 100:
        value = 1.0
    elif distance is None and distance > 100:
        value = 0.50
    elif SPECIES_NM is not None AND F_SEN_ZN_1 = 'No' AND distance > 100:
        value = 0.50
    elif SPECIES_NM is not None AND F_SEN_ZN_1 is None AND distance > 100:
        value = 0.50
    elif SPECIES_NM is not None AND F_SEN_ZN_1 = 'No' AND distance > 100:
        value = 0.50
    elif SPECIES_NM is None AND F_SEN_ZN_1 = 'Yes' AND distance > 100:
        value = 0.75
    elif SPECIES_NM is not None AND F_SEN_ZN_1 = 'Yes' AND distance > 100:
        value = 0.75
    else:
        value = -0.999999999
    return value

and then calling the function

value = getValue(<distance, SPECIES_NM, F_SEN_ZN_1>)

Answer 1

As mentioned by @GermánCarrillo, the use use of CASEs was utilized for my exercise:

-- Cases of fish vulnerability 

-- 1. no data for location
CASE 
    WHEN "distance" IS NULL THEN 0.5
    -- 2. less 100m, fish present, sensitive habitat
    WHEN ("distance" <= 100 AND "SPECIES_NM" is NOT NULL AND "F_SEN_ZN_I" = 'Yes') THEN 1.0
    -- 3. less 100m, fish present, not sensitive habitat
    WHEN ("distance" <= 100 AND "SPECIES_NM" is NOT NULL AND "F_SEN_ZN_I" = 'No') THEN 1.0
    -- 4. less 100m, fish present, no habitat data
    WHEN ("distance" <= 100 AND "SPECIES_NM" is NOT NULL AND "F_SEN_ZN_I" IS NULL) THEN 0.75
    -- 5. less 100m, no fish, sensitive habitat
    WHEN ("distance" <= 100 AND "SPECIES_NM" is NULL AND "F_SEN_ZN_I" = 'Yes') THEN 0.75
    -- 6.less 100m, no fish, not sensitive
    WHEN ("distance" <= 100 AND "SPECIES_NM" is NULL AND "F_SEN_ZN_I" = 'No') THEN 0.5
    -- 7. less 100m, no fish, no habitat data
    WHEN ("distance" <= 100 AND "SPECIES_NM" is NULL AND "F_SEN_ZN_I" IS NULL) THEN 0.5
    -- 8. less 100m, no fish data, sensitive habitat
    WHEN ("distance" <= 100 AND "SPECIES_NM" is NULL AND "F_SEN_ZN_I" = 'Yes') THEN 1.0
    -- 9. less 100m, no fish data, not sensitive
    WHEN ("distance" <= 100 AND "SPECIES_NM" is NULL AND "F_SEN_ZN_I" = 'No') THEN 0.5
    -- 10. less 100m, no fish data, no habitat data
    WHEN ("distance" <= 100 AND "SPECIES_NM" is NULL AND "F_SEN_ZN_I" IS NULL) THEN 0.5
    -- 11. greater than 100m, fish present, sensitive habitat
    WHEN ("distance" >= 100 AND "SPECIES_NM" is NOT NULL AND "F_SEN_ZN_I" = 'Yes') THEN 0.75
    -- 12. greater than 100m, fish present, not sensitive
    WHEN ("distance" >= 100 AND "SPECIES_NM" is NOT NULL AND "F_SEN_ZN_I" = 'No') THEN 0.75
    --13. greater than 100m, fish present, no habitat data
    WHEN ("distance" >= 100 AND "SPECIES_NM" is NOT NULL AND "F_SEN_ZN_I" IS NULL) THEN 0.75
    --14. greater than 100m, no fish, sensitive habitat
    WHEN ("distance" >= 100 AND "SPECIES_NM" is NULL AND "F_SEN_ZN_I" = 'Yes') THEN 0.75
    --15. greater than 100m, no fish, not sensitive
    WHEN ("distance" >= 100 AND "SPECIES_NM" is NULL AND "F_SEN_ZN_I" = 'No') THEN 0.75
    -- 16. greater than 100m, no fish, no habitat data
    WHEN ("distance" >= 100 AND "SPECIES_NM" is NULL AND "F_SEN_ZN_I" IS NULL) THEN 0.5
    -- 17. greater than 100m, no fish data, sensitive habitat
    WHEN ("distance" >= 100 AND "SPECIES_NM" is NULL AND "F_SEN_ZN_I" = 'Yes') THEN 0.75
    -- 18. greater than 100m, no fish data, not sensitive
    WHEN ("distance" >= 100 AND "SPECIES_NM" is NULL AND "F_SEN_ZN_I" = 'No') THEN 0.5
    -- 19. greater than 100m, no fish data, no habitat data
    WHEN ("distance" >= 100 AND "SPECIES_NM" is NULL AND "F_SEN_ZN_I" IS NULL) THEN 0.5 
END