Changing field type with ArcPy?

Question

What I need to do is change data type of a field of a table or feature class. If there are some data, then I need to transfer it, if its possible, if not possible then just set null for that data. I need to do it using python script.

Problems:

Because of before and after changing the data type, field name is same, I can not add new field with same name using arcpy.AddField_management method.
Because of I need to transfer field values from first field to second one, I need to map both data types.

It will be good for me if I can find any ArcPy procedure similar to artwork21's answer to Renaming field using ArcPy?

You might want to vote for this ArcGIS Idea (as if it hasn't gotten enough votes already). — blah238, Feb 22 '13 at 03:44
@blah238: My data is stored in a table/feature class. And the idea is for reordering the fields not changing the data type. — Emi, Feb 22 '13 at 03:55
You misunderstood me. What is your underlying DBMS: Oracle, SQL Server, PostgreSQL, file geodatabase, personal geodatabase, shapefile, etc.? — blah238, Feb 22 '13 at 03:57
You are correct, this is the one I meant: ArcGIS should provide the ability to make changes to field types — blah238, Feb 22 '13 at 04:00
@blah238: it can be a file geodatabase or personal geodatabase or shapefile. — Emi, Feb 22 '13 at 04:02
Can anyone tell me recently whenever I post question, why do I got down vote without telling any reason? please give me the reason, when you are giving me a down vote — Emi, Feb 22 '13 at 04:05
I did not downvote it, but the question does not show much research effort (reads like a "do my homework for me" type question, sorry to say), and could use some minor grammar cleanup. — blah238, Feb 22 '13 at 04:08

blah238 · Accepted Answer · 2013-02-22T04:03:32.013

There are essentially three options for making field schema changes in ArcGIS.

Dropping the whole feature class/table and replacing it completely
Dropping the field/column and replacing it -- this always puts the new column at the end, so not good if field order is important to you.
Modifying column definitions in the underlying DBMS (dangerous, may cause corruption). This last one I wouldn't even go near unless you are in Oracle, and even then you have to be very careful (see this post).

It sounds like you want to go with option 2. The simplest way I can think of to do that is to add an intermediate/temporary column and calculate it from your original column. Then delete the original column, add a new column with the desired field type, calculate the new column from the intermediate column and finally delete the intermediate column.

May be I will go with your 2nd idea. I need to read about it some more. thanks for the idea — Emi, Feb 22 '13 at 04:03

score 4 · Answer 2 · answered Feb 22 '13 at 08:47

4

You could do a simple "Feature Class to Feature Class" conversion. During this you can change field names and types, after that delete the original FC.

answered Feb 22 '13 at 08:47

Torsten

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PolyGeo · Answer 3 · 2016-06-16T22:59:25.020

Depending on your ArcGIS for Desktop version and where you are storing your data, there is a tool called Alter Field (available at all license levels from 10.2.2; only Advanced at 10.2.1) that may be able to help you because it is designed to:

Rename fields and field aliases, or alter field properties.

However, be aware that if you only change the name, and not the alias too, then when you look at the attribute table, what is displayed as that field's heading will be the alias (i.e. the old field name).

To avoid this, which I find confusing, I always change both the name and the alias .

For example, if I want to change the OLDFIELD to be named NEWFIELD then I use something like:

# AlterField_management (in_table, field, {new_field_name}, {new_field_alias})
AlterField_management (r"C:\temp\test.gdb\testFC", "OLDFIELD", "NEWFIELD", "NEWFIELD")

Changing field type with ArcPy?

3 Answers3

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