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Copying/replacing first letter in column of attribute table in ArcMap with field calculator and Python Parser? [on hold]

.everyoneloves__top-leaderboard:empty,.everyoneloves__mid-leaderboard:empty,.everyoneloves__bot-mid-leaderboard:empty margin-bottom:0;

0

How to copy / replace the first letter in a column if that letter is "N" and replace with "C" in the field name "DISTRICT" inside the attribute table in ArcMap using Python inside the field calculator?

arcgis-desktop arcmap field-calculator python-parser

share|improve this question

edited Apr 4 at 19:46

PolyGeo♦

53.9k1781246

asked Apr 4 at 15:38

Anthony StokesAnthony Stokes

947

put on hold as off-topic by Dan C, Kadir Şahbaz, csk, BERA, ahmadhanb Apr 5 at 1:08

This question appears to be off-topic. The users who voted to close gave this specific reason:

• "When seeking help to debug/write/improve code always provide the desired behavior, a specific problem/error and the shortest code (as formatted text, not pictures) needed to reproduce it in the question body. Providing a clear problem statement and a code attempt helps others to help you." – Dan C, Kadir Şahbaz, csk, BERA, ahmadhanb

If this question can be reworded to fit the rules in the help center, please edit the question.

add a comment | 

0

How to copy / replace the first letter in a column if that letter is "N" and replace with "C" in the field name "DISTRICT" inside the attribute table in ArcMap using Python inside the field calculator?

arcgis-desktop arcmap field-calculator python-parser

share|improve this question

edited Apr 4 at 19:46

PolyGeo♦

53.9k1781246

asked Apr 4 at 15:38

Anthony StokesAnthony Stokes

947

put on hold as off-topic by Dan C, Kadir Şahbaz, csk, BERA, ahmadhanb Apr 5 at 1:08

This question appears to be off-topic. The users who voted to close gave this specific reason:

• "When seeking help to debug/write/improve code always provide the desired behavior, a specific problem/error and the shortest code (as formatted text, not pictures) needed to reproduce it in the question body. Providing a clear problem statement and a code attempt helps others to help you." – Dan C, Kadir Şahbaz, csk, BERA, ahmadhanb

If this question can be reworded to fit the rules in the help center, please edit the question.

add a comment | 

How to copy / replace the first letter in a column if that letter is "N" and replace with "C" in the field name "DISTRICT" inside the attribute table in ArcMap using Python inside the field calculator?

arcgis-desktop arcmap field-calculator python-parser

share|improve this question

edited Apr 4 at 19:46

PolyGeo♦

53.9k1781246

asked Apr 4 at 15:38

Anthony StokesAnthony Stokes

947

share|improve this question

edited Apr 4 at 19:46

PolyGeo♦

53.9k1781246

asked Apr 4 at 15:38

Anthony StokesAnthony Stokes

947

share|improve this question

edited Apr 4 at 19:46

PolyGeo♦

53.9k1781246

asked Apr 4 at 15:38

Anthony StokesAnthony Stokes

947

edited Apr 4 at 19:46

PolyGeo♦

53.9k1781246

edited Apr 4 at 19:46

PolyGeo♦

53.9k1781246

asked Apr 4 at 15:38

Anthony StokesAnthony Stokes

947

asked Apr 4 at 15:38

Anthony StokesAnthony Stokes

947

4 Answers
4

active

oldest

votes

4

The general format for overall string replace in Python in the Field Calculator is

= !stringvar!.replace("substring to find", "new substring")

If you want to only change the first initial for all records, you could build this based on a slice of the string.

= "C" + !stringvar![1:]

If you only want to change the first initial if it starts with a "N", then you're getting into conditional statements (if/then) and should wrap this in a function for use within the Field Calculator. Build this in the codebook/pre-Logic script code.

def replaceIfN(fieldtochange):
 if fieldtochange.lower().startswith("n"): # handles both n and N
 return "C" + fieldtochange[1:]
 else: # no change made
 return fieldtochange

Run this with

 = replaceIfN(!DISTRICT!) 

See http://desktop.arcgis.com/en/arcmap/10.3/manage-data/tables/calculate-field-examples.htm

share|improve this answer

answered Apr 4 at 16:23

smillersmiller

2,284217

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  The conditional statement is the solution I was looking for.
  
  – Anthony Stokes
  Apr 4 at 16:32
  

  
  
  
  

add a comment | 

7

You don't even have to write any code!

Simply edit the table and do a find and replace on the selected field.

Example of replacing B with XXX.

Result of replacement

share|improve this answer

answered Apr 4 at 16:19

HornbyddHornbydd

27.1k32958

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  I need to know how to copy / replace the first letter in a column if that letter is "N" and replace with "C" using python inside the field calculator. I don't want to replace every instance of "N". This would require some code.
  
  – Anthony Stokes
  Apr 4 at 16:38
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  Well... if you look at the image, what does Text match say... You can use @Jackson_Dunn's approach if you intend to wrap the field calculate in say modelbuilder. If you just want to replace the first N with C then my approach is less painful and quicker.
  
  – Hornbydd
  Apr 4 at 16:45
  
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  I see what you mean. This is the fastest way without code but I like to always know the python equivalent.
  
  – Anthony Stokes
  Apr 4 at 17:12
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Are imgur images always going to be on the site, or is there a risk of them not loading at some distant point in the future? If the latter, please elaborate on your answer (e.g. Select "Start of Field" for Text match)
  
  – smiller
  Apr 4 at 18:01
  

  
  
  
  


• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  
  I didnt know of find and replace, nice!
  
  – BERA
  Apr 4 at 18:53
  

  
  
  
  

 | 
show 3 more comments

2

You can add a number to the python replace code to determine how many instances to change (in your case just one):

!District!.replace("C", "N", 1)

share|improve this answer

edited Apr 4 at 19:54

PolyGeo♦

53.9k1781246

answered Apr 4 at 18:31

Jackson DunnJackson Dunn

292

New contributor

Jackson Dunn is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Thanks @Jackson Dunn. I'd be curious as to performance between the string replace number of instances vs. string slicing. I suspect in this case it's minimal but may be worth testing on larger fields or more complex replacements.
  
  – smiller
  Apr 4 at 19:52
  

  
  
  
  

add a comment | 

0

Using vbscript instead if you're working in ArcGIS Desktop, The code is:

REPLACE ([DISTRICT],"C","N",1,1)

Where :

• the first 1 equals the line position (first character)


• and the second 1 is amount of characters to change (only need to change one letter per row, not all C's and N's).

share|improve this answer

edited Apr 4 at 19:49

PolyGeo♦

53.9k1781246

answered Apr 4 at 15:54

Jackson DunnJackson Dunn

292

New contributor

Jackson Dunn is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  This is the VB script solution so thank you for that but I was wondering how to solve it using python in the field calculator.
  
  – Anthony Stokes
  Apr 4 at 16:12
  

  
  
  
  

add a comment | 

4

The general format for overall string replace in Python in the Field Calculator is

= !stringvar!.replace("substring to find", "new substring")

If you want to only change the first initial for all records, you could build this based on a slice of the string.

= "C" + !stringvar![1:]

If you only want to change the first initial if it starts with a "N", then you're getting into conditional statements (if/then) and should wrap this in a function for use within the Field Calculator. Build this in the codebook/pre-Logic script code.

def replaceIfN(fieldtochange):
 if fieldtochange.lower().startswith("n"): # handles both n and N
 return "C" + fieldtochange[1:]
 else: # no change made
 return fieldtochange

Run this with

 = replaceIfN(!DISTRICT!) 

See http://desktop.arcgis.com/en/arcmap/10.3/manage-data/tables/calculate-field-examples.htm

share|improve this answer

answered Apr 4 at 16:23

smillersmiller

2,284217

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  The conditional statement is the solution I was looking for.
  
  – Anthony Stokes
  Apr 4 at 16:32
  

  
  
  
  

add a comment | 

4

The general format for overall string replace in Python in the Field Calculator is

= !stringvar!.replace("substring to find", "new substring")

If you want to only change the first initial for all records, you could build this based on a slice of the string.

= "C" + !stringvar![1:]

If you only want to change the first initial if it starts with a "N", then you're getting into conditional statements (if/then) and should wrap this in a function for use within the Field Calculator. Build this in the codebook/pre-Logic script code.

def replaceIfN(fieldtochange):
 if fieldtochange.lower().startswith("n"): # handles both n and N
 return "C" + fieldtochange[1:]
 else: # no change made
 return fieldtochange

Run this with

 = replaceIfN(!DISTRICT!) 

See http://desktop.arcgis.com/en/arcmap/10.3/manage-data/tables/calculate-field-examples.htm

share|improve this answer

answered Apr 4 at 16:23

smillersmiller

2,284217

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  The conditional statement is the solution I was looking for.
  
  – Anthony Stokes
  Apr 4 at 16:32
  

  
  
  
  

add a comment | 

The general format for overall string replace in Python in the Field Calculator is

= !stringvar!.replace("substring to find", "new substring")

If you want to only change the first initial for all records, you could build this based on a slice of the string.

= "C" + !stringvar![1:]

If you only want to change the first initial if it starts with a "N", then you're getting into conditional statements (if/then) and should wrap this in a function for use within the Field Calculator. Build this in the codebook/pre-Logic script code.

def replaceIfN(fieldtochange):
 if fieldtochange.lower().startswith("n"): # handles both n and N
 return "C" + fieldtochange[1:]
 else: # no change made
 return fieldtochange

Run this with

 = replaceIfN(!DISTRICT!) 

See http://desktop.arcgis.com/en/arcmap/10.3/manage-data/tables/calculate-field-examples.htm

share|improve this answer

answered Apr 4 at 16:23

smillersmiller

2,284217

= !stringvar!.replace("substring to find", "new substring")

= "C" + !stringvar![1:]

def replaceIfN(fieldtochange):
 if fieldtochange.lower().startswith("n"): # handles both n and N
 return "C" + fieldtochange[1:]
 else: # no change made
 return fieldtochange

 = replaceIfN(!DISTRICT!) 

share|improve this answer

answered Apr 4 at 16:23

smillersmiller

2,284217

answered Apr 4 at 16:23

smillersmiller

2,284217

answered Apr 4 at 16:23

smillersmiller

2,284217

7

You don't even have to write any code!

Simply edit the table and do a find and replace on the selected field.

Example of replacing B with XXX.

Result of replacement

share|improve this answer

answered Apr 4 at 16:19

HornbyddHornbydd

27.1k32958

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  I need to know how to copy / replace the first letter in a column if that letter is "N" and replace with "C" using python inside the field calculator. I don't want to replace every instance of "N". This would require some code.
  
  – Anthony Stokes
  Apr 4 at 16:38
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  Well... if you look at the image, what does Text match say... You can use @Jackson_Dunn's approach if you intend to wrap the field calculate in say modelbuilder. If you just want to replace the first N with C then my approach is less painful and quicker.
  
  – Hornbydd
  Apr 4 at 16:45
  
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  I see what you mean. This is the fastest way without code but I like to always know the python equivalent.
  
  – Anthony Stokes
  Apr 4 at 17:12
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Are imgur images always going to be on the site, or is there a risk of them not loading at some distant point in the future? If the latter, please elaborate on your answer (e.g. Select "Start of Field" for Text match)
  
  – smiller
  Apr 4 at 18:01
  

  
  
  
  


• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  
  I didnt know of find and replace, nice!
  
  – BERA
  Apr 4 at 18:53
  

  
  
  
  

 | 
show 3 more comments

7

You don't even have to write any code!

Simply edit the table and do a find and replace on the selected field.

Example of replacing B with XXX.

Result of replacement

share|improve this answer

answered Apr 4 at 16:19

HornbyddHornbydd

27.1k32958

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  I need to know how to copy / replace the first letter in a column if that letter is "N" and replace with "C" using python inside the field calculator. I don't want to replace every instance of "N". This would require some code.
  
  – Anthony Stokes
  Apr 4 at 16:38
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  Well... if you look at the image, what does Text match say... You can use @Jackson_Dunn's approach if you intend to wrap the field calculate in say modelbuilder. If you just want to replace the first N with C then my approach is less painful and quicker.
  
  – Hornbydd
  Apr 4 at 16:45
  
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  I see what you mean. This is the fastest way without code but I like to always know the python equivalent.
  
  – Anthony Stokes
  Apr 4 at 17:12
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Are imgur images always going to be on the site, or is there a risk of them not loading at some distant point in the future? If the latter, please elaborate on your answer (e.g. Select "Start of Field" for Text match)
  
  – smiller
  Apr 4 at 18:01
  

  
  
  
  


• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  
  I didnt know of find and replace, nice!
  
  – BERA
  Apr 4 at 18:53
  

  
  
  
  

 | 
show 3 more comments

You don't even have to write any code!

Simply edit the table and do a find and replace on the selected field.

Example of replacing B with XXX.

Result of replacement

share|improve this answer

answered Apr 4 at 16:19

HornbyddHornbydd

27.1k32958

share|improve this answer

answered Apr 4 at 16:19

HornbyddHornbydd

27.1k32958

answered Apr 4 at 16:19

HornbyddHornbydd

27.1k32958

answered Apr 4 at 16:19

HornbyddHornbydd

27.1k32958

2

You can add a number to the python replace code to determine how many instances to change (in your case just one):

!District!.replace("C", "N", 1)

share|improve this answer

edited Apr 4 at 19:54

PolyGeo♦

53.9k1781246

answered Apr 4 at 18:31

Jackson DunnJackson Dunn

292

New contributor

Jackson Dunn is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Thanks @Jackson Dunn. I'd be curious as to performance between the string replace number of instances vs. string slicing. I suspect in this case it's minimal but may be worth testing on larger fields or more complex replacements.
  
  – smiller
  Apr 4 at 19:52
  

  
  
  
  

add a comment | 

2

You can add a number to the python replace code to determine how many instances to change (in your case just one):

!District!.replace("C", "N", 1)

share|improve this answer

edited Apr 4 at 19:54

PolyGeo♦

53.9k1781246

answered Apr 4 at 18:31

Jackson DunnJackson Dunn

292

New contributor

Jackson Dunn is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Thanks @Jackson Dunn. I'd be curious as to performance between the string replace number of instances vs. string slicing. I suspect in this case it's minimal but may be worth testing on larger fields or more complex replacements.
  
  – smiller
  Apr 4 at 19:52
  

  
  
  
  

add a comment | 

You can add a number to the python replace code to determine how many instances to change (in your case just one):

!District!.replace("C", "N", 1)

share|improve this answer

edited Apr 4 at 19:54

PolyGeo♦

53.9k1781246

answered Apr 4 at 18:31

Jackson DunnJackson Dunn

292

New contributor

Jackson Dunn is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

!District!.replace("C", "N", 1)

share|improve this answer

edited Apr 4 at 19:54

PolyGeo♦

53.9k1781246

answered Apr 4 at 18:31

Jackson DunnJackson Dunn

292

New contributor

Jackson Dunn is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

edited Apr 4 at 19:54

PolyGeo♦

53.9k1781246

edited Apr 4 at 19:54

PolyGeo♦

53.9k1781246

answered Apr 4 at 18:31

Jackson DunnJackson Dunn

292

New contributor

Jackson Dunn is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

answered Apr 4 at 18:31

Jackson DunnJackson Dunn

292

0

Using vbscript instead if you're working in ArcGIS Desktop, The code is:

REPLACE ([DISTRICT],"C","N",1,1)

Where :

• the first 1 equals the line position (first character)


• and the second 1 is amount of characters to change (only need to change one letter per row, not all C's and N's).

share|improve this answer

edited Apr 4 at 19:49

PolyGeo♦

53.9k1781246

answered Apr 4 at 15:54

Jackson DunnJackson Dunn

292

New contributor

Jackson Dunn is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  This is the VB script solution so thank you for that but I was wondering how to solve it using python in the field calculator.
  
  – Anthony Stokes
  Apr 4 at 16:12
  

  
  
  
  

add a comment | 

0

Using vbscript instead if you're working in ArcGIS Desktop, The code is:

REPLACE ([DISTRICT],"C","N",1,1)

Where :

• the first 1 equals the line position (first character)


• and the second 1 is amount of characters to change (only need to change one letter per row, not all C's and N's).

share|improve this answer

edited Apr 4 at 19:49

PolyGeo♦

53.9k1781246

answered Apr 4 at 15:54

Jackson DunnJackson Dunn

292

New contributor

Jackson Dunn is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  This is the VB script solution so thank you for that but I was wondering how to solve it using python in the field calculator.
  
  – Anthony Stokes
  Apr 4 at 16:12
  

  
  
  
  

add a comment | 

Using vbscript instead if you're working in ArcGIS Desktop, The code is:

REPLACE ([DISTRICT],"C","N",1,1)

Where :

• the first 1 equals the line position (first character)


• and the second 1 is amount of characters to change (only need to change one letter per row, not all C's and N's).

share|improve this answer

edited Apr 4 at 19:49

PolyGeo♦

53.9k1781246

answered Apr 4 at 15:54

Jackson DunnJackson Dunn

292

New contributor

Jackson Dunn is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

REPLACE ([DISTRICT],"C","N",1,1)

share|improve this answer

edited Apr 4 at 19:49

PolyGeo♦

53.9k1781246

answered Apr 4 at 15:54

Jackson DunnJackson Dunn

292

New contributor

Jackson Dunn is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

edited Apr 4 at 19:49

PolyGeo♦

53.9k1781246

edited Apr 4 at 19:49

PolyGeo♦

53.9k1781246

answered Apr 4 at 15:54

Jackson DunnJackson Dunn

292

New contributor

Jackson Dunn is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

answered Apr 4 at 15:54

Jackson DunnJackson Dunn

292