topic Re: Copying only text from a string field to a new field in Python Questions

Copying only text from a string field to a new field

PieterSnyders — Thu, 19 Jul 2012 09:22:35 GMT

Good day,

I know this is probably a stupid question. I am working with a river data set and the labeling field is a string field containing text (river names) and integer (river codes). I want to copy only the text (river names) to a new field. How can I do this with the field calculator... any help will be appreciated.

Regards,

P

Re: Copying only text from a string field to a new field

JakeSkinner — Thu, 19 Jul 2012 09:41:15 GMT

Are the text and integer values separated by a space? You can most likely use the .split command to do this. However, this will be a little more difficult if any of the river names contain spaces. Are all the integer values the same length (i.e. 100, 220, 354, etc)? It may be best to provide a screen shot of how the field looks in your attribute table.

Re: Copying only text from a string field to a new field

PieterSnyders — Thu, 19 Jul 2012 09:48:05 GMT

I have attached two sections of the field

Re: Copying only text from a string field to a new field

PieterSnyders — Thu, 19 Jul 2012 09:49:13 GMT

Some of the river names do have spaces

Re: Copying only text from a string field to a new field

JakeSkinner — Sat, 11 Dec 2021 15:55:44 GMT

Here is an example on how you can do this:

Codeblock:

def update(field):
  if field[0] in str(range(0, 9)) or field[0] == '#':
    pass
  else:
    return field

Field=

update(!TAG!)

Be sure 'Python' is checked on at the top of the field calculator. Here is a screen shot.
[ATTACH=CONFIG]16236[/ATTACH]

Re: Copying only text from a string field to a new field

PieterSnyders — Thu, 19 Jul 2012 10:31:18 GMT

Thank you, that worked partially, this is what is left:

Re: Copying only text from a string field to a new field

KimOllivier — Sat, 11 Dec 2021 15:55:47 GMT

Use a Regular Expression to match names with letters to make a selection, then just do a copy on selected records. Regular expressions are supported in Python and are a very powerful text manipulation tool.

Maybe we could assume that no names start with a digit, so you could reverse the search to look for any integer
But if you didn't, an expression re.match('[A-Za-z ]+',inField) would allow any combination of letters and spaces

# pseudocode (not run) for interactive Python window
# NOT field calculator (keep that for modelbuilder....)
import arcpy
import re
arcpy.env.workspace = "your_gdb_path"
cur = arcpy.UpdateCursor("table1")
for row in cur:
    m = re.match('[0-9]+',row.inField) # matches any value beginning with integer string of digits
    if not m : # ie not nothing found
        row.nameCopy = m.string
        cur.updateRow(row) # must not forget this or doesn't write to file
del cur # close cursor

# nameCopy is target field, inField is source field

Re: Copying only text from a string field to a new field

PieterSnyders — Sat, 11 Dec 2021 15:55:49 GMT

Use a Regular Expression to match names with letters to make a selection, then just do a copy on selected records. Regular expressions are supported in Python and are a very powerful text manipulation tool.

Maybe we could assume that no names start with a digit, so you could reverse the search to look for any integer
But if you didn't, an expression re.match('[A-Za-z ]+',inField) would allow any combination of letters and spaces
# pseudocode (not run) for interactive Python window
# NOT field calculator (keep that for modelbuilder....)
import arcpy
import re
arcpy.env.workspace = "your_gdb_path"
cur = arcpy.UpdateCursor("table1")
for row in cur:
    m = re.match('[0-9]+',row.inField) # matches any value beginning with integer string of digits
    if not m : # ie not nothing found
        row.nameCopy = m.string
        cur.updateRow(row) # must not forget this or doesn't write to file
del cur # close cursor

# nameCopy is target field, inField is source field

Where should this code go... I am very new to this and quite confused lol

Re: Copying only text from a string field to a new field

JakeSkinner — Thu, 19 Jul 2012 10:49:32 GMT

Thank you, that worked partially, this is what is left:

Can you send a screen shot of what you entered in the Field Calculator. It looks like the code did the opposite of what you are looking to accomplish. It calculated all the text values that begin with a number and '#' sign, and not the values that begin with a character.

Re: Copying only text from a string field to a new field

PieterSnyders — Thu, 19 Jul 2012 10:58:27 GMT

Can you send a screen shot of what you entered in the Field Calculator. It looks like the code did the opposite of what you are looking to accomplish. It calculated all the text values that begin with a number and '#' sign, and not the values that begin with a character.

Here is the snapshot

Re: Copying only text from a string field to a new field

JakeSkinner — Thu, 19 Jul 2012 11:12:11 GMT

You will want to specify the field that has the current values in the update() function. So, change:

 update(!Label_Field!)

to:

update(!TAG!)

This will calculate the values, that begin with a character, from the TAG field to the LABEL_FIELD.

Re: Copying only text from a string field to a new field

PieterSnyders — Thu, 19 Jul 2012 11:23:17 GMT

Success! Thank you! Now I will just have to figure out exactly how this works lol

Re: Copying only text from a string field to a new field

PieterSnyders — Thu, 19 Jul 2012 11:29:06 GMT

Funny enough two numerical values remained: 92 and 9390553

Re: Copying only text from a string field to a new field

JakeSkinner — Sat, 11 Dec 2021 15:55:52 GMT

That was my mistake, the code should have been:

def update(field):
  if field[0] in str(range(0, 10)) or field[0] == '#':
    pass
  else:
    return field

What this code is doing is checking the first character of each value. If the first character is a number within the range of 0 - 10, or if the character is a '#' sign it will pass this row. If the character is a letter, it will update the row in the new field with that value.

Re: Copying only text from a string field to a new field

PieterSnyders — Thu, 19 Jul 2012 11:39:06 GMT

Thank you for the explanation, will speed up my work! Really need to learn more of this very handy!