Checking for number of shapefiles in directory using Python?

Question

I want to test:

1. to see whether or not ONE AND ONLY ONE shapefile (which will be based on a filename wildcard) exists in a directory.
2. Add these shapefiles to a list
3. Use this list variable as an input to merge_managment function.

I already know how to walk through directories and pick out those filenames but not how to do the above.

I was thinking something like:

rootDir = "\homePath"
featureinput1 = "path"
newOnlyShpList = []
for dirPath, dirNames, fileNames in os.walk(rootDir):
    for file in fileNames:
       if fnmatch.fnmatch(file, "*" + "2012" + "*" + ".shp")== True ##AND IF ONE SHAPEFILE EXISTS BY ITSELF IN DIRECTORY:##
          ##append to newOnlyShpList
          arcpy.Merge_managment([featureinput1, newOnlyShpList], "OutputHere")
       elif
          ##ignore if greater than one shapefile

All I know about is the arcpy .exists function but all that does is return a boolean on whether any shapefile exists. Maybe I need to check just for 1 .shp extension and it has nothing to do with arcpy?

Answer 1

Check the glob library:

import os
import glob
path = "c:\\my\\dir"

flist = glob.glob(os.path.join(path,"shapefile*"))  <- Notice the *

>>> flist 
["c:\\my\\dir\shapefile.prj","c:\\my\\dir\shapefile.shp",...]

If you want just the fname without the path attached:

 os.path.basename(flist[0]) 
 >>> shapefile.prj

if you want just the file name without the extension:

os.path.basename(flist[0]).split(".")[0]
>>> shapefile

Also if the list is empty, then the file doesn't exist:

if flist not:
    print "File not found"
    break #or os.exit(1)

Edit: Also to check for the only filename in path :

import os
import glob
path = "c:\\my\\dir"

flist = glob.glob(os.path.join(path,"shapefile*"))  <- Notice the *
mlist = []
for file in flist:
    if os.path.basename(file).split(".")[0] not in mlist:
        mlist.append(os.path.basename(file).split(".")[0])
if len(mlist)>1: #(More than filename)
    break

To check if only one shapefile in the dir:

 def file_check(path):
      """Returns true if in path there is only one basename"""
      import os
      mlist = [] 
      for file in os.listdir(path):
          if os.path.basename(file).split(".")[0] not in mlist:
                mlist.append(os.path.basename(file).split(".")[0]
   if len(mlist)>1:
            return True
    else:
            return False

Answer 2

ArcGIS has a built in function to list all shapefiles in a folder:

import arcpy
from arcpy import env    

arcpy.env.workspace = 'E:/myFolder/'
fcs = arcpy.ListFeatureClasses("*.shp", "")

fcs is an array that stores the name of all of the shapefiles in the folder myFolder. For example, to print out all of the shapefiles in myFolder you can just do this:

for shp in fcs:    
    print shp

[just moving this from the comment] To test if the list of files contains only the file that you want in this folder, you could use the condition:

if 'myfile' in fcs and len(fcs)==1:
       print 'true'

Answer 3

To answer this question nowadays (since ArcGIS 10.1 SP1) I would recommend the answer from @djq in conjunction with using arcpy.da.Walk to walk the folder structure:

Generate data names in a directory/database structure by walking the tree top-down or bottom-up. Each directory/workspace yields a tuple of three: directory path, directory names, and file names.