How to Refer to a Null value with ArcPy Expressions
I feel like this might be a bit of a simple answer but I can't figure out how to refer to Null values in a field using an expression in python. I've tried using the following as well as = None and =Null but nothing has worked yet:
ScoreCondition = "Cond_Score(!"+Condition+"!)"
codeblock1 = """def Cond_Score(cond):
if cond > 90:
return 1
elif cond >= 71 and cond <= 90:
return 2
elif cond >= 51 and cond <= 70:
return 3
elif cond >= 20 and cond <= 50:
return 4
elif cond < 20:
return 5
elif cond is None:
return 1"""
arcpy arcmap field-calculator python-parser null
edited 4 hours ago
PolyGeo♦
53.3k1779238
asked 5 hours ago
Adam ReedAdam Reed
192
add a comment |
I feel like this might be a bit of a simple answer but I can't figure out how to refer to Null values in a field using an expression in python. I've tried using the following as well as = None and =Null but nothing has worked yet:
ScoreCondition = "Cond_Score(!"+Condition+"!)"
codeblock1 = """def Cond_Score(cond):
if cond > 90:
return 1
elif cond >= 71 and cond <= 90:
return 2
elif cond >= 51 and cond <= 70:
return 3
elif cond >= 20 and cond <= 50:
return 4
elif cond < 20:
return 5
elif cond is None:
return 1"""
arcpy arcmap field-calculator python-parser null
edited 4 hours ago
PolyGeo♦
53.3k1779238
asked 5 hours ago
Adam ReedAdam Reed
192
1
One equals sign is for assigning values. To test for equality, use two of them:==
– Dan C
4 hours ago
1
can't you just put an Else: for the last elif?
– klewis
2 hours ago
What kind of feature storage is your data? Not every data type can store a None or Null value. Shapefiles can't, numeric Null becomes 0 and string Null becomes '' (an empty string). In geodatabases (personal, file or enterprise) Null values can be stored (test with cond == None as @DanC said) but your implementation of ScoreCondition = "Cond_Score(!"+Condition+"!)" doesn't look quite right, can you show your line where you call Cond_Score in CalculateField_management, it's possible you may be parsing your numbers as strings.
– Michael Stimson
2 hours ago
add a comment |
I feel like this might be a bit of a simple answer but I can't figure out how to refer to Null values in a field using an expression in python. I've tried using the following as well as = None and =Null but nothing has worked yet:
ScoreCondition = "Cond_Score(!"+Condition+"!)"
codeblock1 = """def Cond_Score(cond):
if cond > 90:
return 1
elif cond >= 71 and cond <= 90:
return 2
elif cond >= 51 and cond <= 70:
return 3
elif cond >= 20 and cond <= 50:
return 4
elif cond < 20:
return 5
elif cond is None:
return 1"""
arcpy arcmap field-calculator python-parser null
edited 4 hours ago
PolyGeo♦
53.3k1779238
asked 5 hours ago
Adam ReedAdam Reed
192
I feel like this might be a bit of a simple answer but I can't figure out how to refer to Null values in a field using an expression in python. I've tried using the following as well as = None and =Null but nothing has worked yet:
ScoreCondition = "Cond_Score(!"+Condition+"!)"
codeblock1 = """def Cond_Score(cond):
if cond > 90:
return 1
elif cond >= 71 and cond <= 90:
return 2
elif cond >= 51 and cond <= 70:
return 3
elif cond >= 20 and cond <= 50:
return 4
elif cond < 20:
return 5
elif cond is None:
return 1"""
arcpy arcmap field-calculator python-parser null
arcpy arcmap field-calculator python-parser null
edited 4 hours ago
PolyGeo♦
53.3k1779238
asked 5 hours ago
Adam ReedAdam Reed
192
edited 4 hours ago
PolyGeo♦
53.3k1779238
asked 5 hours ago
Adam ReedAdam Reed
192
edited 4 hours ago
PolyGeo♦
53.3k1779238
edited 4 hours ago
PolyGeo♦
53.3k1779238
edited 4 hours ago
PolyGeo♦
53.3k1779238
53.3k1779238
asked 5 hours ago
Adam ReedAdam Reed
192
asked 5 hours ago
Adam ReedAdam Reed
192
asked 5 hours ago
Adam ReedAdam Reed
192
192
1
One equals sign is for assigning values. To test for equality, use two of them:==
– Dan C
4 hours ago
1
can't you just put an Else: for the last elif?
– klewis
2 hours ago
What kind of feature storage is your data? Not every data type can store a None or Null value. Shapefiles can't, numeric Null becomes 0 and string Null becomes '' (an empty string). In geodatabases (personal, file or enterprise) Null values can be stored (test with cond == None as @DanC said) but your implementation of ScoreCondition = "Cond_Score(!"+Condition+"!)" doesn't look quite right, can you show your line where you call Cond_Score in CalculateField_management, it's possible you may be parsing your numbers as strings.
– Michael Stimson
2 hours ago
add a comment |
1
One equals sign is for assigning values. To test for equality, use two of them:==
– Dan C
4 hours ago
1
can't you just put an Else: for the last elif?
– klewis
2 hours ago
What kind of feature storage is your data? Not every data type can store a None or Null value. Shapefiles can't, numeric Null becomes 0 and string Null becomes '' (an empty string). In geodatabases (personal, file or enterprise) Null values can be stored (test with cond == None as @DanC said) but your implementation of ScoreCondition = "Cond_Score(!"+Condition+"!)" doesn't look quite right, can you show your line where you call Cond_Score in CalculateField_management, it's possible you may be parsing your numbers as strings.
– Michael Stimson
2 hours ago
1
1
One equals sign is for assigning values. To test for equality, use two of them:
==– Dan C
4 hours ago
One equals sign is for assigning values. To test for equality, use two of them:
==– Dan C
4 hours ago
1
1
can't you just put an Else: for the last elif?
– klewis
2 hours ago
can't you just put an Else: for the last elif?
– klewis
2 hours ago
What kind of feature storage is your data? Not every data type can store a None or Null value. Shapefiles can't, numeric Null becomes 0 and string Null becomes '' (an empty string). In geodatabases (personal, file or enterprise) Null values can be stored (test with cond == None as @DanC said) but your implementation of ScoreCondition = "Cond_Score(!"+Condition+"!)" doesn't look quite right, can you show your line where you call Cond_Score in CalculateField_management, it's possible you may be parsing your numbers as strings.
– Michael Stimson
2 hours ago
What kind of feature storage is your data? Not every data type can store a None or Null value. Shapefiles can't, numeric Null becomes 0 and string Null becomes '' (an empty string). In geodatabases (personal, file or enterprise) Null values can be stored (test with cond == None as @DanC said) but your implementation of ScoreCondition = "Cond_Score(!"+Condition+"!)" doesn't look quite right, can you show your line where you call Cond_Score in CalculateField_management, it's possible you may be parsing your numbers as strings.
– Michael Stimson
2 hours ago
add a comment |
2 Answers
2
active
oldest
votes
Your problem is that in Python 2 None is less than everything.
>>> None < 20
True
>>> None < numpy.nan
True
>>> None < float('-inf')
True
>>> None < 'Everything'
True
Notes:
- In ArcGIS Pro (Python 3) you'll get a
TypeErrorusing a numeric comparison operator withNonewhich will help avoid this issue. - This doesn't apply to shapefiles as the old dBase format .dbf that stores the attribute table doesn't support null values
In your expression, Python is returning True when evaluating the
elif cond < 20 clause when cond IS really None so never gets to the elif cond is None: clause.
So the following will work because it tests for None first:
def Cond_Score(cond):
if cond is None:
return 1
elif cond > 90:
return 1
elif cond >= 71 and cond <= 90:
return 2
elif cond >= 51 and cond <= 70:
return 3
elif cond >= 20 and cond <= 50:
return 4
elif cond < 20:
return 5
answered 3 hours ago
LukeLuke
28.8k252102
add a comment |
I've confirmed all three of the following work when using the Field Calculator. Could it be an error somewhere else? Does the code work for the other condition?
if cond == None:
return 1
if cond is None:
return 2
if not cond:
return 3
answered 3 hours ago
MBuieMBuie
91
add a comment |
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2 Answers
2
active
oldest
votes
2 Answers
2
active
oldest
votes
active
oldest
votes
active
oldest
votes
Your problem is that in Python 2 None is less than everything.
>>> None < 20
True
>>> None < numpy.nan
True
>>> None < float('-inf')
True
>>> None < 'Everything'
True
Notes:
- In ArcGIS Pro (Python 3) you'll get a
TypeErrorusing a numeric comparison operator withNonewhich will help avoid this issue. - This doesn't apply to shapefiles as the old dBase format .dbf that stores the attribute table doesn't support null values
In your expression, Python is returning True when evaluating the
elif cond < 20 clause when cond IS really None so never gets to the elif cond is None: clause.
So the following will work because it tests for None first:
def Cond_Score(cond):
if cond is None:
return 1
elif cond > 90:
return 1
elif cond >= 71 and cond <= 90:
return 2
elif cond >= 51 and cond <= 70:
return 3
elif cond >= 20 and cond <= 50:
return 4
elif cond < 20:
return 5
answered 3 hours ago
LukeLuke
28.8k252102
add a comment |
Your problem is that in Python 2 None is less than everything.
>>> None < 20
True
>>> None < numpy.nan
True
>>> None < float('-inf')
True
>>> None < 'Everything'
True
Notes:
- In ArcGIS Pro (Python 3) you'll get a
TypeErrorusing a numeric comparison operator withNonewhich will help avoid this issue. - This doesn't apply to shapefiles as the old dBase format .dbf that stores the attribute table doesn't support null values
In your expression, Python is returning True when evaluating the
elif cond < 20 clause when cond IS really None so never gets to the elif cond is None: clause.
So the following will work because it tests for None first:
def Cond_Score(cond):
if cond is None:
return 1
elif cond > 90:
return 1
elif cond >= 71 and cond <= 90:
return 2
elif cond >= 51 and cond <= 70:
return 3
elif cond >= 20 and cond <= 50:
return 4
elif cond < 20:
return 5
answered 3 hours ago
LukeLuke
28.8k252102
add a comment |
Your problem is that in Python 2 None is less than everything.
>>> None < 20
True
>>> None < numpy.nan
True
>>> None < float('-inf')
True
>>> None < 'Everything'
True
Notes:
- In ArcGIS Pro (Python 3) you'll get a
TypeErrorusing a numeric comparison operator withNonewhich will help avoid this issue. - This doesn't apply to shapefiles as the old dBase format .dbf that stores the attribute table doesn't support null values
In your expression, Python is returning True when evaluating the
elif cond < 20 clause when cond IS really None so never gets to the elif cond is None: clause.
So the following will work because it tests for None first:
def Cond_Score(cond):
if cond is None:
return 1
elif cond > 90:
return 1
elif cond >= 71 and cond <= 90:
return 2
elif cond >= 51 and cond <= 70:
return 3
elif cond >= 20 and cond <= 50:
return 4
elif cond < 20:
return 5
answered 3 hours ago
LukeLuke
28.8k252102
Your problem is that in Python 2 None is less than everything.
>>> None < 20
True
>>> None < numpy.nan
True
>>> None < float('-inf')
True
>>> None < 'Everything'
True
Notes:
- In ArcGIS Pro (Python 3) you'll get a
TypeErrorusing a numeric comparison operator withNonewhich will help avoid this issue. - This doesn't apply to shapefiles as the old dBase format .dbf that stores the attribute table doesn't support null values
In your expression, Python is returning True when evaluating the
elif cond < 20 clause when cond IS really None so never gets to the elif cond is None: clause.
So the following will work because it tests for None first:
def Cond_Score(cond):
if cond is None:
return 1
elif cond > 90:
return 1
elif cond >= 71 and cond <= 90:
return 2
elif cond >= 51 and cond <= 70:
return 3
elif cond >= 20 and cond <= 50:
return 4
elif cond < 20:
return 5
answered 3 hours ago
LukeLuke
28.8k252102
edited 13 mins ago
answered 3 hours ago
LukeLuke
28.8k252102
answered 3 hours ago
LukeLuke
28.8k252102
answered 3 hours ago
LukeLuke
28.8k252102
28.8k252102
add a comment |
add a comment |
I've confirmed all three of the following work when using the Field Calculator. Could it be an error somewhere else? Does the code work for the other condition?
if cond == None:
return 1
if cond is None:
return 2
if not cond:
return 3
answered 3 hours ago
MBuieMBuie
91
add a comment |
I've confirmed all three of the following work when using the Field Calculator. Could it be an error somewhere else? Does the code work for the other condition?
if cond == None:
return 1
if cond is None:
return 2
if not cond:
return 3
answered 3 hours ago
MBuieMBuie
91
add a comment |
I've confirmed all three of the following work when using the Field Calculator. Could it be an error somewhere else? Does the code work for the other condition?
if cond == None:
return 1
if cond is None:
return 2
if not cond:
return 3
answered 3 hours ago
MBuieMBuie
91
I've confirmed all three of the following work when using the Field Calculator. Could it be an error somewhere else? Does the code work for the other condition?
if cond == None:
return 1
if cond is None:
return 2
if not cond:
return 3
answered 3 hours ago
MBuieMBuie
91
answered 3 hours ago
MBuieMBuie
91
answered 3 hours ago
MBuieMBuie
91
answered 3 hours ago
MBuieMBuie
91
91
add a comment |
add a comment |
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1
One equals sign is for assigning values. To test for equality, use two of them:
==– Dan C
4 hours ago
1
can't you just put an Else: for the last elif?
– klewis
2 hours ago
What kind of feature storage is your data? Not every data type can store a None or Null value. Shapefiles can't, numeric Null becomes 0 and string Null becomes '' (an empty string). In geodatabases (personal, file or enterprise) Null values can be stored (test with cond == None as @DanC said) but your implementation of ScoreCondition = "Cond_Score(!"+Condition+"!)" doesn't look quite right, can you show your line where you call Cond_Score in CalculateField_management, it's possible you may be parsing your numbers as strings.
– Michael Stimson
2 hours ago