TypeError: float() argument must be a string or a number, not 'function' – Python/Sklearn

I have the following code snippet from a program called Flights.py

...
#Load the Dataset
df = dataset
df.isnull().any()
df = df.fillna(lambda x: x.median())

# Define X and Y
X = df.iloc[:, 2:124].values
y = df.iloc[:, 136].values
X_tolist = X.tolist()

# Splitting the dataset into the Training set and Test set
from sklearn.cross_validation import train_test_split
X_train, X_test, y_train, y_test = train_test_split(X, y, test_size = 0.2, random_state = 0)

# Feature Scaling
from sklearn.preprocessing import StandardScaler
sc = StandardScaler()
X_train = sc.fit_transform(X_train)
X_test = sc.transform(X_test)

The second to last line is throwing the following error:

Traceback (most recent call last):

  File "<ipython-input-14-d4add2ccf5ab>", line 3, in <module>
    X_train = sc.fit_transform(X_train)

  File "/Users/<username>/anaconda/lib/python3.6/site-packages/sklearn/base.py", line 494, in fit_transform
    return self.fit(X, **fit_params).transform(X)

  File "/Users/<username>/anaconda/lib/python3.6/site-packages/sklearn/preprocessing/data.py", line 560, in fit
    return self.partial_fit(X, y)

  File "/Users/<username>/anaconda/lib/python3.6/site-packages/sklearn/preprocessing/data.py", line 583, in partial_fit
    estimator=self, dtype=FLOAT_DTYPES)

  File "/Users/<username>/anaconda/lib/python3.6/site-packages/sklearn/utils/validation.py", line 382, in check_array
    array = np.array(array, dtype=dtype, order=order, copy=copy)

TypeError: float() argument must be a string or a number, not 'function'

My dataframe df is of size (22587, 138)

I was taking a look at the following question for inspiration:

TypeError: float() argument must be a string or a number, not 'method' in Geocoder

I tried the following adjustment:

# Feature Scaling
from sklearn.preprocessing import StandardScaler
sc = StandardScaler()
X_train = sc.fit_transform(X_train.as_matrix)
X_test = sc.transform(X_test.as_matrix)

Which resulted in the following error:

AttributeError: 'numpy.ndarray' object has no attribute 'as_matrix'

I'm currently at a loss for how to scan thru the dataframe and find/convert the offending entries.