Python TypeError: Cannot do slice stop value indexing on <class 'pandas.core.index.Int64Index'>

Am getting a Type Error, while trying to filter some past data using python and pandas. Here's the error

TypeError: cannot do slice stop value indexing on < class 'pandas.core.index.Int64Index'> with these indexers [327.0] of < type 'float'>

Code

# 65% of training data
ratio = 0.65
train_data_df = df_replace[:round(dataset_length*ratio)]  
test_data_df = df_replace[-(1-round(dataset_length*ratio)):]  

# Create Respected CSV
train_data_df.to_csv('Train.csv',index=False)
test_data_df.to_csv('Test.csv',index=False)

Additional Info

The code is working upto creating a new CSV file India_in_Tests_Filter.csv that has more than 450 rows and 3 columns as follows:

Result Toss Bat

Lost   won  1st 
Won    won  2nd

While India_in_Tests.csv have more than 450 rows and 7 columns.

So folks, any thoughts on that?