Changing single character in attribute table with ArcPy?

Question

I was trying to speed up my data processing, and I was wondering, which would be the python code, that could browse through my shapefiles, and find special single characters (which I define) in attribute table in string fields, and replace them with defined characters.

For example, I have shapefiles, in my "D:\GIS_One" folder. All of the shapefiles have few string(text) fields in their attribute tables. For example, value in some of the fields are "Day&Night", "Mix!" "Über". In this example, I would like to replace "&" with "_" , "!" with "One" and "Ü" with "U". Just the single characters, not the whole words, since I have another code to change the whole words. I am just looking for a code to do a single character replacement.

I already tried with How to iterate fields and remove Null values and spaces but could not manage to work it out. Also, I know how to to it with Field Calculator, and Excel/LibreOffice, but I am looking for a Python solution so I could speed up my work.

EDIT: As Michael asked, I worked on a first two codes, and now I am working on a third provided from a posted link. Here is working code:

>>> import arcpy
    fc = ["D:\GIS_One\Ride.shp", "D:\GIS_One\Unknown.shp" ]
    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)):
                if not row[i]:
                    row[i] == ""
                elif row[i] == "&":
                    row[i] == "_"
                elif row[i] == "!":
                    row[i] == "1"
                elif row[i] == "Ü":
                    row[i] == "U"
            cursor.updateRow(row)
print "Processing complete"

I get this error:

Runtime error Traceback (most recent call last): File "", line 3, in File "c:\program files\arcgis\desktop10.1\arcpy\arcpy__init__.py", line 1075, in ListFields return gp.listFields(dataset, wild_card, field_type) File "c:\program files\arcgis\desktop10.1\arcpy\arcpy\geoprocessing_base.py", line 344, in listFields self._gp.ListFields(*gp_fixargs(args, True))) IOError: "['D:/GIS_One/Ride.shp', 'D:/GIS_One/Unknown.shp']" does not exist

And if I try with one feature class from database, with this code:

>>> import arcpy
    fc = "D:\GIS_Temp\TEST.gdb\ONE"
    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)):
               if not row[i]:
                    row[i] == ""
                elif row[i] == "&":
                    row[i] == "_"
                elif row[i] == "!":
                    row[i] == "One"
                elif row[i] == "Ü":
                    row[i] == "U"    
            cursor.updateRow(row)
print "Processing complete"

I get this error:

Runtime error Traceback (most recent call last): File "", line 5, in TypeError: 'field_names' must be string or non empty sequence of strings

It would be really helpful if i could manage to make the code to work on shapefiles.

Answer 1

You need to use the str.replace() to replace the characters in your field values.

Also needed to put a for fc in fcs: to loop through your shapefiles, and remove the square brackets from around fieldList in your cursor (this is what is giving you the error 'field_names' must be string or non empty sequence of strings)

And note the u in front of u"Ü" so that you don't get a decode error.

import arcpy
fcs = [r"D:\GIS_One\Ride.shp", r"D:\GIS_One\Unknown.shp" ]

for fc in fcs:
    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)):
                    newFieldvalue = row[i].replace("&","_").replace("!","1").replace(u"Ü","U")
                    row[i] = newFieldvalue
                cursor.updateRow(row)

print "Processing complete"

Answer 2

I see a couple things going on here. In your first code example you tried to set fc to a list of two feature classes. The listFields function expects a single feature class, not a list. If you wanted to do that, you'd have to iterate through your feature class list. The next big thing I see is that those funny characters that you're trying to get rid of are confusing python. Best to figure out the ascii code for those funny characters and feed them in with the chr function. (I found this table of ascii codes with a quick google search.) And then one more note about the ascii codes. Python 2 only supported using the chr function on ascii codes up to 128. That umlat U is 220, so we have to get a little fancy with it to make it work. I believe the code below should run just fine on both shapefiles and feature classes in geodatabase.

import arcpy
fcLst = [r"D:\GIS_One\Ride.shp", r"D:\GIS_One\Unknown.shp" ]
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(chr(38),"_")
                    row[i] = row[i].replace("!","1")
                    row[i] = row[i].replace(unicode(chr(220), encoding="latin1"),"U")
                    cursor.updateRow(row)

Answer 3

So, I will post an answer, which could be useful to other users which are using central European characters. I think it could work other characters and encoding for other languages, but the encoding and characters must be changed, depending of the language. This is example for central european, and character Đ. This site could be useful for the codes.

>>> import arcpy
    fcLst = [r"PATH"] # Path to your shapefile
    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(unicode(chr(209), encoding="CP852"),"D") # For number of character, use the code from the site in link, and for the encoding, use desired encoding for your characters. This is example for Central European characters, for replacing Đ with D. 
                        cursor.updateRow(row)