topic Re: Create variable with Cursor and write it in a text file with Python in Python Questions

Create variable with Cursor and write it in a text file with Python

KONPETROV — Sat, 11 Dec 2021 08:43:22 GMT

Hi, i am trying to create three variables from a table and write them in a text file with Python. These variables are values from the first row of three fields. I tried it with Search Cursor but i can get only the first variable, i don't know why. Next i am trying to do the same with a folder of polylines taking the first row of 2 fields using the same text i created above but unsuccesfully. Any suggestion would be great. Thanks a lot. This is my code:

import arcpy
import os
from arcpy import env

arcpy.env.workspace = "c:/Win/Sik"
input = "s3s2c10"
fields = ['X', 'Y', 'MOSAIC']

#NEW TXT FILE "MOON"
outFile = open("c:/Win/Sik/moon.text", "w")
with arcpy.da.SearchCursor(input, fields, 'OID = 1') as cursor:
    X = row[0]
    Y = row[1]
    IPSOS = row[2]

outFile.write('x is '+str(X)+'meters,'\n' Y is'+str(Y)+'and '\n' ipsos is'+str(IPSOS))
outfile.close()

import arcpy
import os
arcpy.env.workspace = "c:Win/Sik/True
outFile = open("c:/Win/Sik/moon.text", "w")
featureclasses = arcpy.ListFeatureClasses("Truelines", "Polyline", "")
for fc in featureclasses:
    TIME = row[0]
    DISTANCE = row[1] 
outFile.write( '\n''\n' 'TIME is '+str(TIME)+'meters,'\n' and DISTANCE is'+str(DISTANCE)+'meters'
outfile.close()

Re: Create variable with Cursor and write it in a text file with Python

LukeWebb — Sat, 11 Dec 2021 08:43:25 GMT

For the 1st part (and the 2nd but well get to that later), you dont define 'row' anywhere, so I dont know where its getting the variable from!

To correct try adding the line 'for row in cursor:' as I have below:

import arcpy
import os
from arcpy import env

arcpy.env.workspace = "c:/Win/Sik"
input = "s3s2c10"
fields = ['X', 'Y', 'MOSAIC']

#NEW TXT FILE "MOON"
outFile = open("c:/Win/Sik/moon.text", "w")
with arcpy.da.SearchCursor(input, fields, 'OID = 1') as cursor:
    for row in cursor:
        X = row[0]
        Y = row[1]
        IPSOS = row[2]

outFile.write('x is '+str(X)+'meters,'\n' Y is'+str(Y)+'and '\n' ipsos is'+str(IPSOS))
outfile.close()

Re: Create variable with Cursor and write it in a text file with Python

JakeSkinner — Sat, 11 Dec 2021 08:43:27 GMT

Hi Kon,

For your search cursor, try the following:

with arcpy.da.SearchCursor(input, fields, 'OID = 1') as cursor:
    for row in cursor:
        X = row[0] 
        Y = row[1] 
        IPSOS = row[2]

For the folder of polyline feature classes, if there are many feature classes you are trying to iterate through, you will want to use a wildcard. You existing syntax will only find a feature class called 'Truelines'. You may want to add try '*'. This will iterate through all of the feature classes in the workspace. Ex:

featureclasses = arcpy.ListFeatureClasses("*", "Polyline", "")  
for fc in featureclasses:
    with arcpy.da.SearchCursor(fc, fields) as cursor:
        for row in cursor:
            TIME = row[0]  
            DISTANCE = row[1]   
            outFile.write( '\n''\n' 'TIME is '+str(TIME)+'meters,'\n' and DISTANCE is'+str(DISTANCE)+'meters'  
outfile.close()

Re: Create variable with Cursor and write it in a text file with Python

KONPETROV — Thu, 28 May 2015 19:32:33 GMT

Luke i am getting a

Runtime error Traceback (most recent call last): File "", line 12, in RuntimeError: A column was specified that does not exist.

but i cannot understand why

Re: Create variable with Cursor and write it in a text file with Python

KONPETROV — Thu, 28 May 2015 19:58:57 GMT

Jake with the first block i am getting the same error as in Luke:

Runtime error Traceback (most recent call last): File "", line 12, in RuntimeError: A column was specified that does not exist.

For the second block of code, "Trueline" is my wildcard. And i have ap problem with the last line cause i am getting an error

Parsing error SyntaxError: invalid syntax (line 12)

Re: Create variable with Cursor and write it in a text file with Python

DarrenWiens2 — Sat, 11 Dec 2021 08:43:30 GMT

Check that your input shapefile indeed has a field called 'OID' and not the more usual 'FID' field.

Compare:

>>> arcpy.env.workspace = r"C:\junk"
... input = "points"
... fields = ['heading','distance']
... with arcpy.da.SearchCursor(input,fields,"OID = 1") as cursor:
...     for row in cursor:
...         print row
...         
Runtime error 
Traceback (most recent call last):
  File "<string>", line 5, in <module>
RuntimeError: A column was specified that does not exist.
>>> arcpy.env.workspace = r"C:\junk"
... input = "points"
... fields = ['heading','distance']
... with arcpy.da.SearchCursor(input,fields,"FID = 1") as cursor:
...     for row in cursor:
...         print row
...         
(192, 533)

Re: Create variable with Cursor and write it in a text file with Python

KONPETROV — Thu, 28 May 2015 20:53:44 GMT

Οh, god. Yes you are right about that, table has a Rowid starting from 1 and Polyline an FID starting from 0. But i am still getting an error Parsing error SyntaxError: unexpected character after line continuation character (line 17)

when i run it inside outfile to write it in my text.

Re: Create variable with Cursor and write it in a text file with Python

DarrenWiens2 — Thu, 28 May 2015 20:57:44 GMT

I don't believe you need all the quotes around the \n's:

outFile.write('x is ' + str(X) + 'meters,\n Y is' + str(Y) + 'and \n ipsos is' + str(IPSOS))

Re: Create variable with Cursor and write it in a text file with Python

KONPETROV — Thu, 28 May 2015 21:48:11 GMT

and of course you were right again! I have two last questions, can i have these two scripts together as a tool because these are two different workspaces.? How can i pass also the name of each shp ?

Re: Create variable with Cursor and write it in a text file with Python

OwenEarley — Thu, 28 May 2015 22:07:30 GMT

To pass in the names of the shapefiles you can use arcpy.GetParameterAsText(). For an outline of how to do this see these pages:

Using parameters you could also pass in the different workspaces and switch between them when required.

Re: Create variable with Cursor and write it in a text file with Python

KONPETROV — Sat, 11 Dec 2021 08:43:32 GMT

Thank you Owen. It's just that i haven't used again two different workspaces inside a script.

Except from that for the iteration of shapefiles this is the code:

import arcpy  
import os
from arcpy import env
arcpy.env.workspace = "c:Win/Sik/Routes"  
outFile = open("c:/Win/Sik/moon.text", "w")  
featureclasses = arcpy.ListFeatureClasses("RT", "Polyline", "")
for fc in featureclasses:
    fields = ['DISTANCE', 'DURATION']
    with arcpy.da.SearchCursor(fc, fields, "FID = 0") as cursor:  
        for row in cursor:  
            TIME = row[0]    
            DISTANCE = row[1]     
outFile.write('TIME is ' + str(TIME) + 'meters,\n Y is' + str(DISTANCE) + 'and \n ipsos is' + str(DISTANCE))    
outfile.close()

but i get back that error

Runtime error

Traceback (most recent call last):

File "<string>", line 7, in <module>

TypeError: 'NoneType' object is not iterable

although i have defined the type of shapefiles

Re: Create variable with Cursor and write it in a text file with Python

KONPETROV — Thu, 28 May 2015 22:45:32 GMT

What does is it mean, "is not iterable"? How can that be?

Re: Create variable with Cursor and write it in a text file with Python

BillDaigle — Thu, 28 May 2015 23:22:10 GMT

I think the arcpy.ListFeatureClasses command is returning None (which is not iterable) because the workspace is not getting set correctly in line 4. Try updating line 4 to:

arcpy.env.workspace = "c:/Win/Sik/Routes"

Re: Create variable with Cursor and write it in a text file with Python

KONPETROV — Sat, 11 Dec 2021 08:43:36 GMT

i did it already Daigle, but still remains. I also applied this

import arcpy  
... import os
... from arcpy import env
... arcpy.env.workspace = "c:/Win/Sik/Routes"  
... outFile = open("c:/Win/Sik/moon.text", "w")  
... featureclasses = arcpy.ListFeatureClasses("RT", "Polyline")
... for fc in featureclasses:
...     fields = ['DISTANCE', 'DURATION']
...     with arcpy.da.SearchCursor(fc, fields, "FID = 0") as cursor:  
...         for row in cursor:
...             outFile.write('distance is ' + str(row[0]) + 'meters,\n duration is' + str(row[1])
... outFile.close()

but either it returns nothing or overwrites the previous results from text file leaving an empty file

Re: Create variable with Cursor and write it in a text file with Python

KONPETROV — Fri, 29 May 2015 01:33:56 GMT

I think i found it! The wildcard(*) for God. Now can i put these to scripts to be together as one or the second will overwrite the first?

Re: Create variable with Cursor and write it in a text file with Python

curtvprice — Sat, 11 Dec 2021 08:43:39 GMT

Two issues with OID = 1 worth noting I think:

1. You can get the name o the object ID field (which can vary by data source and sometimes by workflow) you can do this:

OIDField  = arcpy.Describe(lyr).OIDFieldName

2. The first row can be object ID zero or one, depending on data source. If what you want the first row, I'd do this instead:

row = arcpy.da.SearchCursor(input, fields).next()
print row