"Found input variables with inconsistent numbers of samples" Have I done something wrong during the train_test_split?

I am trying to logistic Regression Model, and run some test but I keep getting this error. Not really sure what I have done differently to everyone else

from sklearn import preprocessing
X = df.iloc[:,:len(df.columns)-1]
y = df.iloc[:,len(df.columns)-1]ere

This is how I am separating my columns

X_train, X_test, y_train, y_test = train_test_split(X, y, test_size=0.2, random_state=0)

TTS

logReg = LogisticRegression(n_jobs=-1)
logReg.fit(X_train, y_train)

y_pred = logReg.predict(X_train)

mae = mean_absolute_error(y_test, y_pred)
print("MAE:" , mae)

ValueError                                Traceback (most recent call last)
Cell In [112], line 1
----> 1 mae = mean_absolute_error(y_test, y_pred)
      2 print("MAE:" , mae)

File ~\AppData\Local\Programs\Python\Python310\lib\site-packages\sklearn\metrics\_regression.py:196, in mean_absolute_error(y_true, y_pred, sample_weight, multioutput)
    141 def mean_absolute_error(
    142     y_true, y_pred, *, sample_weight=None, multioutput="uniform_average"
    143 ):
    144     """Mean absolute error regression loss.
    145 
    146     Read more in the :ref:`User Guide <mean_absolute_error>`.
   (...)
    194     0.85...
    195     """
--> 196     y_type, y_true, y_pred, multioutput = _check_reg_targets(
    197         y_true, y_pred, multioutput
    198     )
    199     check_consistent_length(y_true, y_pred, sample_weight)
    200     output_errors = np.average(np.abs(y_pred - y_true), weights=sample_weight, axis=0)

File ~\AppData\Local\Programs\Python\Python310\lib\site-packages\sklearn\metrics\_regression.py:100, in _check_reg_targets(y_true, y_pred, multioutput, dtype)
     66 def _check_reg_targets(y_true, y_pred, multioutput, dtype="numeric"):
     67     """Check that y_true and y_pred belong to the same regression task.
     68 
     69     Parameters
   (...)
     98         correct keyword.
     99     """
--> 100     check_consistent_length(y_true, y_pred)
    101     y_true = check_array(y_true, ensure_2d=False, dtype=dtype)
    102     y_pred = check_array(y_pred, ensure_2d=False, dtype=dtype)

File ~\AppData\Local\Programs\Python\Python310\lib\site-packages\sklearn\utils\validation.py:387, in check_consistent_length(*arrays)
    385 uniques = np.unique(lengths)
    386 if len(uniques) > 1:
--> 387     raise ValueError(
    388         "Found input variables with inconsistent numbers of samples: %r"
    389         % [int(l) for l in lengths]
    390     )

ValueError: Found input variables with inconsistent numbers of samples: [25404, 101612]

I thought it was the way I split the columns but that doesn't seem to be the issue It works when the test size is 50/50 but no other test size works

You are comparing the predicted labels for the train set with the labels for the test set, which are of different sizes, hence the error.

Replace

y_pred = logReg.predict(X_train)

with

y_pred = logReg.predict(X_test)