topic Re: Removing/Replacing specific characters from a field in Python Questions

Removing/Replacing specific characters from a field

GIS_geek — Wed, 31 Oct 2018 22:54:10 GMT

I am trying to remove specific characters from a field called CCTV_SLID. The field I am working with looks like this CLMH123W456MH123W455, STMH123W457, SIMH123W458, SYMH123W459. I am trying to remove the prefixes which are CL, ST, SI, and SY. I have the following script and get a IOError: "C" does not exist error. Any help would be appreciated. Thanks.

# Remove prefix from CCTV_SLID

fcLst = "C:/Desktop/CCTV.gdb/GravityMain"
for fc in fcLst:
    fieldList = [f.name for f in arcpy.ListFields(fc) if f.type == "String"]
    if fieldList:
        with arcpy.da.UpdateCurson(fc, fieldList) as cursor:
            for row in cursor:
                for i in range(len(fieldList)):
                    row = row.replace("CL"," ")
                    cursor.updateRow(row)

Re: Removing/Replacing specific characters from a field

DanPatterson_Retired — Wed, 31 Oct 2018 23:13:42 GMT

/blogs/dan_patterson/2016/08/14/script-formatting would really help because line numbers can be referred to

Re: Removing/Replacing specific characters from a field

GIS_geek — Sat, 11 Dec 2021 07:36:54 GMT

import arcpy

# Remove prefix from CCTV_SLID
print("Replace and remove prefix from CCTV_SLID.")
fcLst = "C:/Desktop/CCTV.gdb/GravityMain"
for fc in fcLst:
    fieldList = [f.name for f in arcpy.ListFields(fc) if f.type == "String"]
    if fieldList:
        with arcpy.da.UpdateCursor(fc, fieldList) as cursor:
            for row in cursor:
                for i in range(len(fieldList)):
                    row[i] = row[i].replace("CL"," ")
                    cursor.updateRow(row)
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Re: Removing/Replacing specific characters from a field

DanPatterson_Retired — Sat, 11 Dec 2021 07:36:57 GMT

 fcLst = "C:/Desktop/CCTV.gdb/GravityMain"
for fc in fcLst:
    print(fc)
    
C
:
/
D
e
s

...... snip .......‍‍‍‍‍‍‍‍‍‍‍‍

you don't have a list for the fcList

you want

fcLst = ["C:/Desktop/CCTV.gdb/GravityMain"]
for fc in fcLst:
    print(fc)
    
C:/Desktop/CCTV.gdb/GravityMain‍‍‍‍‍

Re: Removing/Replacing specific characters from a field

GIS_geek — Thu, 01 Nov 2018 00:06:30 GMT

Dan,

I updated the script and I get the following error

row = row.replace("CL","")
AttributeError: 'NoneType' object has no attribute 'replace'

Re: Removing/Replacing specific characters from a field

JoeBorgione — Thu, 01 Nov 2018 00:48:57 GMT

None means your value for row is null. You'll need to 'trap' for that condition with an if conditional or a try/except block.

Re: Removing/Replacing specific characters from a field

DanPatterson_Retired — Sat, 11 Dec 2021 07:37:00 GMT

if row is not None:
    Do the work here
‍‍

if row[i] not in (None, "", "anything else you want to check for"):
    Do good stuff here‍‍

Re: Removing/Replacing specific characters from a field

curtvprice — Sat, 11 Dec 2021 07:37:02 GMT

Here's my preferred approach (which Joe mentioned).

In Python some times it is easier to just let an error happen instead of coding a check for every possible thing that can go wrong (in your case, that the text field has a null value).

I also fixed this so it will only remove the prefix, that is, your prefix must be the first two chars of the text field value.

import arcpy

print("Replace and remove prefix from any and all text fields.")
fcLst = ["C:/Desktop/CCTV.gdb/GravityMain"]
for fc in fcLst:
    fieldList = [f.name for f in arcpy.ListFields(fc) if f.type == "String"]
    if fieldList:
        with arcpy.da.UpdateCursor(fc, fieldList) as cursor:
            for row in cursor:
                for i in range(len(fieldList)):
                    try:
                        if row[i][:2] in ["CL", "ST", "SI","SY"]:
                            row[i] = row[i][2:]
                            cursor.updateRow(row)
                    except:
                        pass
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Re: Removing/Replacing specific characters from a field

GIS_geek — Thu, 01 Nov 2018 19:46:41 GMT

Thank you all for your help. I really appreciate it.

Re: Removing/Replacing specific characters from a field

JoshuaBixby — Fri, 02 Nov 2018 13:56:30 GMT

I suggest out-denting your cursor update call, Line #13, by one level. You can wait until you have updated the entire row before committing it.

Re: Removing/Replacing specific characters from a field

curtvprice — Sat, 11 Dec 2021 07:37:05 GMT

Joshua, you are so right. Unnecessarily calling an update could massively slow things down. Here's a fix that outdents it even more so only one update would be called, and only if a change was made:

import arcpy

print("Replace and remove prefix from any and all text fields.")
fcLst = ["C:/Desktop/CCTV.gdb/GravityMain"]
for fc in fcLst:
    fieldList = [f.name for f in arcpy.ListFields(fc) if f.type == "String"]
    if fieldList:
        with arcpy.da.UpdateCursor(fc, fieldList) as cursor:
            for row in cursor:
                rowmod = False
                for i in range(len(fieldList)):
                    try:
                        if row[i][:2] in ["CL", "ST", "SI","SY"]:
                            row[i] = row[i][2:]
                            rowmod = True
                    except:
                        pass
                if rowmod:
                    cursor.updateRow(row)‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍