How to fix the index value that I use for X_test and y_test?

I am writing code for SVR. Therefore, I have generated my code as the requirements. But I am stuck on writing codes for the index of for-loop of X_test and y_test. I have to write code as it should be associated with the line in the datasets just next to the X_train and y_train. So their index should be +1 of the ending index of X_train and y_train.

For Example:

• In the first iteration (i.e. when i=0), we are using the first 1000 rows for training and the next row (i.e. the 1001st row) for testing

• In the second iteration (i.e. when i=1), we are using the rows from 1 to 1001 for training and the next row (i.e. the 1002nd row) for testing

• In the third iteration (i.e. when i=2), we are using the rows from 2 to 1002 for training and the next row (i.e. the 1003rd row) for testing and so on.

My full code:

import pandas as pd
import numpy as np

# Make fake dataset
dataset = pd.DataFrame(data= np.random.rand(2000,22))
dataset['age'] = np.random.randint(2, size=2000)

# Separate the target from the other features
target = dataset['age']
data = dataset.drop('age', axis = 1)

X_train, y_train = data.loc[:1000], target.loc[:1000]

X_test,  y_test  = data.loc[1001], target.loc[1001] 

X_test = np.array(X_test).reshape(1, -1)
print(X_test.shape)

SupportVectorRefModel = SVR()
SupportVectorRefModel.fit(X_train, y_train)

y_pred = SupportVectorRefModel.predict(X_test)
y_pred

y_pred_list = []
y_test_list = []


for i in range(1, 2000):

    X_train, y_train = dataset.iloc[i:1000+i], target.iloc[i:1000+i]
    X_test, y_test = dataset.iloc[i], target.iloc [i]


    X_test = np.array(X_test).reshape(1, -1)
    print(X_test.shape)

    SupportVectorRefModel = SVR()
    SupportVectorRefModel.fit(X_train, y_train)
    y_pred = SupportVectorRefModel.predict(X_test)

    y_pred_list.append(y_pred)

    y_test_list.append(y_test)

print(y_test_list, y_pred_list)

I want to update my code on this below:

 X_test, y_test = dataset.iloc[i], target.iloc [i]

So how may I update this index line as an above requirement?

for i in range(0, 999):

    X_train, y_train = data.iloc[i:(999 + i)], target.iloc[i:(999 + i)]
    X_test, y_test = data.iloc[i + 1000], target.iloc [i + 1000]