Counting a layer in multi MXD using ArcPy

Question

I try to count how many times the layer "frame" occurs in 3 MXD files.

The layer "frame" (this is the layer name in the table of contents) occur in "project1" (this is the first MXD file)- 1 time.

In "project2"- it occur 2 times.

In "project3"- it occur 3 times.

I'm using this python code:

import arcpy,os,sys,string
import arcpy.mapping
from arcpy import env

env.workspace = r"G:\desktop\Project"
counter = 0
for mxdname in arcpy.ListFiles("*.mxd"):
    print mxdname 
    mxd = arcpy.mapping.MapDocument(r"G:\desktop\Project\\" + mxdname)
    df = arcpy.mapping.ListDataFrames(mxd, "Layers")[0]
    dfList = arcpy.mapping.ListDataFrames(mxd, "*")
    for df in dfList:
        for lyr in arcpy.mapping.ListLayers(mxd, "", df):                                   
            if lyr.name == "frame":
                counter = counter + 1
    print counter
    mxd.save()
del mxd

But i get this incorrect result:

>>> 
project1.mxd
1
project2.mxd
4
project3.mxd
6
>>> 

What am I doing wrong?

Answer 1

You should reset your counter variable to 0 every time you iterate over a new mxd, otherwise counter will count the cumulative occurences of 'frame' layers. Create a new counter variable for each iterated mxd by moving it inside the for loop (it will overwrite the previous one):

import arcpy,os,sys,string
import arcpy.mapping
from arcpy import env

env.workspace = r"G:\desktop\Project"
for mxdname in arcpy.ListFiles("*.mxd"):
    counter = 0
    print mxdname 
    mxd = arcpy.mapping.MapDocument(r"G:\desktop\Project\\" + mxdname)
    df = arcpy.mapping.ListDataFrames(mxd, "Layers")[0]
    dfList = arcpy.mapping.ListDataFrames(mxd, "*")
    for df in dfList:
        for lyr in arcpy.mapping.ListLayers(mxd, "", df):                                   
            if lyr.name == "frame":
                counter = counter + 1
    print counter
    mxd.save()
del mxd

Answer 2

As @GISGe says, you need to reset the counter inside the loop.

Also, instead of

        for lyr in arcpy.mapping.ListLayers(mxd, "", df):
            if lyr.name == "frame":
                counter = counter + 1

You could 1) use the wildcard argument in ListLayers, and 2) just check the length of the returned list.

counter += len(arcpy.mapping.ListLayers(mxd, "frame", df)

I'm not sure what this line is doing btw, as df is overwritten in the loop below it.

    df = arcpy.mapping.ListDataFrames(mxd, "Layers")[0]