I am trying to buffer multiple feature classes from a directory but I keep getting the same error message.

JohnnyMonds

import arcpy

# Set workspace for listing
arcpy.env.workspace = r"T:\chastain\PrgGIS\World"
# Get a list of all feature classes
fcs = arcpy.ListFeatureClasses("*")
# Loop through the list
for fc in fcs:
#print names
print("These feature classes are in the World folder", fc)
Output = fc + "Buff"
arcpy.Buffer_analysis(fc, Output, "100 Meters")

ERROR 000670: output Output Feature Class is same as input Input Features
Failed to execute (Buffer).

JohnnyMonds

the program is supposed to get the names, print them, buffer them and then to a new output. so it looks like it is stopping on the buffer end. So now I have changed the Output and it looks like it is trying to work. 

Output = r"C:\Users\johnny.monds\Desktop\Test" +fc[:-4] + "_Buff.shp"
arcpy.Buffer_analysis(fc, Output, "100 Meters")
These feature classes are in the World folder Cities.shp
These feature classes are in the World folder Country.shp
Traceback (most recent call last):
File "<string>", line 12, in <module>
File "c:\program files\arcgis\pro\Resources\arcpy\arcpy\analysis.py", line 1101, in Buffer
raise e
File "c:\program files\arcgis\pro\Resources\arcpy\arcpy\analysis.py", line 1098, in Buffer
retval = convertArcObjectToPythonObject(gp.Buffer_analysis(*gp_fixargs((in_features, out_feature_class, buffer_distance_or_field, line_side, line_end_type, dissolve_option, dissolve_field, method), True)))
File "c:\program files\arcgis\pro\Resources\arcpy\arcpy\geoprocessing\_base.py", line 506, in <lambda>
return lambda *args: val(*gp_fixargs(args, True))
arcgisscripting.ExecuteError: Failed to execute. Parameters are not valid.

ERROR 000732: Input Features: Dataset Country.shp does not exist or is not supported
Failed to execute (Buffer).