pyth-network_pyth-crosschain/apps/developer-hub/content/docs/entropy/request-callback-variants.mdx

---
title: Request Callback Variants
description: Different ways to request random numbers with Pyth Entropy
---

The [`IEntropyV2`](https://github.com/pyth-network/pyth-crosschain/blob/main/target_chains/ethereum/entropy_sdk/solidity/IEntropyV2.sol) interface provides multiple variants of the `requestV2` function:

## 1. Basic request

```solidity
function requestV2() external payable returns (uint64 assignedSequenceNumber);
```

This is the simplest variant that requests entropy using the default provider and default gas settings. Uses in-contract PRNG for the user contribution to randomness.

Use this when you want the most straightforward implementation and don't need to customize provider or gas parameters.

### Example

```solidity
function requestBasicRandomNumber() external payable {
    // Get the fee for the default provider and gas limit
    uint256 fee = entropy.getFeeV2();

    require(msg.value >= fee, "Insufficient fee");

    // Request randomness with default settings
    uint64 sequenceNumber = entropy.requestV2{value: fee}();
}
```

## 2. Request with custom gas limit

```solidity
function requestV2(
    uint32 gasLimit
) external payable returns (uint64 assignedSequenceNumber);
```

This variant allows you to specify a custom gas limit for the callback function execution. Uses in-contract PRNG for the user contribution.

Use this when your `entropyCallback` function has complex logic that requires more gas than the default amount, or when you want to optimize gas usage by setting a lower limit for simple callbacks.

### Example

```solidity
function requestWithCustomGas() external payable {
    uint32 customGasLimit = 150000; // Custom gas limit for callback

    // Get fee for the custom gas limit
    uint256 fee = entropy.getFeeV2(customGasLimit);

    require(msg.value >= fee, "Insufficient fee");

    // Request with custom gas limit
    uint64 sequenceNumber = entropy.requestV2{value: fee}(customGasLimit);
}
```

## 3. Request with custom provider

```solidity
function requestV2(
    address provider
) external payable returns (uint64 assignedSequenceNumber);
```

This variant allows you to specify a custom entropy provider instead of using the default one.

## 4. Full custom request

```solidity
function requestV2(
    address provider,
    uint32 gasLimit,
    bytes32 userRandomNumber
) external payable returns (uint64 assignedSequenceNumber);
```

This is the most flexible variant that allows you to specify all parameters: custom provider, custom gas limit, and user random number.