How do I iterate through an entire directory and select only one class from a multi-class file in Python?

I could use some help iterating through a directory with multi-class files. Each sample contains two classes (for example, the first sample in my database is 1001, and this file includes 1001.dat and 1001.hea), and I want to iterate through my directory and access all .dat files separately from .hea files. Right now, simply iterating through the directory produces a File-Not-Found error.

I'll supply additional source code to give this some context, but first let me show you where I'm stuck.

Using a PhysioNet ECG database, the goal right now is to analyze every .dat file (my example below implements the Dickey-Fuller test, using adfuller from statsmodels.tsa.stattools). I have uploaded my data onto Google colab using the following:

from google.colab import files
uploaded = files.upload()

I am able to access a specific sample from my database easily. For example, if I want to read a sample using WFDB, I can do this without a problem:

wfdb.rdsamp('1001') #1001 is the name of the first sample in my directory

But when I try to iterate through all of these samples, I run into an issue. Here is what I have so far:

for dat in uploaded:
     file = wfdb.rdsamp(dat) #this is where I get the error (below)

At the commented line, I get the following error:

FileNotFoundError: [Errno 2] No such file or directory: '/content/1001.dat.hea'

I believe this is because each file contains two classes, as you can see when I print the type of my file...

Sourcecode:

print(type(uploaded)) #print directory 'uploaded' type (declared in first code block)
for dat in uploaded:  #iterate through directory 'uploaded'
  print(type(dat))    #print file type

Result:

<class 'dict'>
<class 'str'>
<class 'str'>

So, what I want to do is specify the first class 'str' (which is .dat). I only need to use the data contained in 1001.dat, etc. I just don't know how to specify this in Python.

Now, as promised, some more code for more context.

All this stuff works:

#get records. 
sample = '1001' #first sample in database
record = wfdb.rdrecord(sample)                  #read record
FHR = (wfdb.rdsamp(sample))[0][:,0]             #FHR with 0's; FHR = fetal heart rate
newFHR = [i for i in FHR if i > 0]              #FHR without values <= 0

#plot sample record
wfdb.plot_wfdb(record = record, title = sample)

DF_test_result = adfuller(FHR)     #Dickey-Fuller Test

#print results
print ("Results with values <= 0")
print ( "ADF:")
ADF = DF_test_result[0]
print(ADF, "\n")

DF_test_result = adfuller(newFHR)  #Dickey-Fuller Test

#print results
print ("Results with values > 0")
print ( "ADF:")
ADF = DF_test_result[0]
print(ADF, "\n")

This is what I'm working on now. My syntax might not be entirely correct for the body of my for loop (again, I'm a Python newbie) but I can figure out the rest if I can access the correct samples for each iteration:

#declare arrays for adf & pvals
adf = []
pvals = []

#get records
for dat in uploaded:
  file = wfdb.rdsamp(dat) #ERROR IS HERE
  FHR = file[0][:,0]                              #FHR with 0's
  newFHR = [i for i in FHR if i > 0]              #FHR without 0's

  DF_test_result = adfuller(newFHR)               #Dickey-Fuller Test
  adf.append(DF_test_result[0])                   #add adf
  pvals.append(DF_test_result[1])                 #add pvals

Thank you, and absolutely let me know how I could have formatted this post better. I am still learning how to post useful questions on this platform. This is my 3rd question ever on StackOverflow.