"IndexError: too many indices for array" appearing when creating a train test split

I am creating a Neural Network and currently I am working on the; train, test split section using:

import csv
import math
import numpy as np 
import pandas as pd
from keras.models import Sequential
from keras.layers import Dense
import datetime
import matplotlib.pyplot as plt
from sklearn.model_selection import train_test_split

X1 = Values[1:16801] #16,800 values

train_size = int(len(X1) * 0.67)
test_size = len(X1) - train_size

train, test = X1[0:train_size,:], X1[train_size:len(X1),:]
print(len(train), len(test))

I have 16,800 values for X1 which look like:

[0.03454225 0.02062136 0.00186715 ... 0.92857565 0.64930691 0.20325924]

My traceback error message is:

IndexError                                Traceback (most recent call last)
<ipython-input-16-8cadae12af2c> in <module>()
     69 test_size = len(X1) - train_size
     70 
---> 71 train, test = X1[0:train_size,:], X1[train_size:len(X1),:]
     72 print(len(train), len(test))
     73 

IndexError: too many indices for array

I'm not sure why this could be,If anyone can help, it would be really appreciated.