setting environment in arcpy

[sunny]

In arcpy module, when I set the workspace it seems it doesn't work properly and I get a runtime error as below.

import arcpy
#set the path of the data
arcpy.env.workspace='C:\\test'

#using a buffer function that give me an error
arcpy.Buffer_analysis('chah.shp','C:\\test\\chah_buf1.shp','100 Meters')

Runtime error Traceback (most recent call last): File "<string>", line 1, in <module> File "c:\program files (x86)\arcgis\desktop10.4\arcpy\arcpy\analysis.py", line 692, in Buffer raise e ExecuteError: ERROR 000732: Input Features: Dataset chah.shp does not exist or is not supported


#using a buffer function that works fine
arcpy.Buffer_analysis('C:\\test\\chah.shp','C:\\test\\chah_buf1.shp','100 Meters')

[sunny]

import arcpy
#set the path of the data
arcpy.env.workspace='C:\\test'

#using a buffer function that give me an error
arcpy.Buffer_analysis('chah.shp','C:\\test\\chah_buf1.shp','100 Meters')

Error:
Traceback (most recent call last):
  File "C:/test/t.py", line 7, in <module>
    arcpy.Buffer_analysis('chah.shp','C:\\test\\chah_buf1.shp','100 Meters')
  File "C:\Program Files (x86)\ArcGIS\Desktop10.4\ArcPy\arcpy\analysis.py", line 692, in Buffer
    raise e
ExecuteError: Failed to execute. Parameters are not valid.
ERROR 000732: Input Features: Dataset chah.shp does not exist or is not supported
Failed to execute (Buffer).