# Difference between exec() and eval() functions

Both functions have a common objective: **to execute Python code from the string input or code object**. Even though they both have the same objective, `exec()` and `eval()` are not the same.

### Return Values

The `exec()` function doesn't return any value whereas the `eval()` function returns a value computed from the expression.

```python
expression = "3 + 5"

result_eval = eval(expression)
print(result_eval)

result_exec = exec(expression)
print(result_exec)
```

When we run this code, we'll get `8` and `None`. This means that `eval(expression)` evaluated the result and stored it inside `result_eval` whereas `exec(expression)` returned nothing, so the value `None` gets stored into `result_exec`.

```bash
8
None
```

### Execution

The `exec()` function is capable of executing multi-line and multi-statment code, it doesn't matter whether the code is simple, complex, has loops and conditions, classes, and functions.

On the other hand, the `eval()` function is restricted to executing the single-line code which might be a simple or complex expression.

```python
expression = """
for x in range(5):
    print(x, end=" ")
"""

exec(expression)
eval(expression)
```

Look at this code, we have a multi-line code that prints numbers up to the given range. The `exec(expression)` will execute it and display the result but the `eval(expression)` will display the error.

```bash
0 1 2 3 4
SyntaxError: invalid syntax
```

However, if we convert the same expression into a single line as the following, the `eval(expression)` will not throw any error.

```bash
expression = "[print(x, end=' ') for x in range(5)]"
eval(expression)

--------------------
0 1 2 3 4
```

### Summary

| eval() | exec() |
| --- | --- |
| Returns a value | Doesn't return any value |
| Executes a single expression, it might be simple or complex | Capable of executing multi-statement and multi-line expressions containing loops, conditions, functions, and classes |
| Use `eval()` when you need to evaluate a single expression and use its result. | Use `exec()` when you need to execute complex code blocks or multiple statements. |

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**That's all for now**

**Keep Coding✌✌**