# pythonnet - Python for .NET
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Python for .NET is a package that gives Python programmers nearly
seamless integration with the .NET Common Language Runtime (CLR) and
provides a powerful application scripting tool for .NET developers.
It allows Python code to interact with the CLR, and may also be used to
embed Python into a .NET application.
## Calling .NET code from Python
Python for .NET allows CLR namespaces to be treated essentially
as Python packages.
```python
import clr
from System import String
from System.Collections import *
```
To load an assembly, use the `AddReference` function in the `clr` module:
```python
import clr
clr.AddReference("System.Windows.Forms")
from System.Windows.Forms import Form
```
## Embedding Python in .NET
- All calls to python should be inside
a `using (Py.GIL()) {/* Your code here */}` block.
- Import python modules using `dynamic mod = Py.Import("mod")`,
then you can call functions as normal, eg `mod.func(args)`.
- Use `mod.func(args, Py.kw("keywordargname", keywordargvalue))`
to apply keyword arguments.
- All python objects should be declared as `dynamic` type.
- Mathematical operations involving python and literal/managed types must
have the python object first, eg. `np.pi * 2` works, `2 * np.pi` doesn't.
### Example
```csharp
static void Main(string[] args)
{
using (Py.GIL())
{
dynamic np = Py.Import("numpy");
Console.WriteLine(np.cos(np.pi * 2));
dynamic sin = np.sin;
Console.WriteLine(sin(5));
double c = np.cos(5) + sin(5);
Console.WriteLine(c);
dynamic a = np.array(new List { 1, 2, 3 });
Console.WriteLine(a.dtype);
dynamic b = np.array(new List { 6, 5, 4 }, Py.kw("dtype", np.int32));
Console.WriteLine(b.dtype);
Console.WriteLine(a * b);
Console.ReadKey();
}
}
```
Output:
```c
1.0
-0.958924274663
-0.6752620892
float64
int32
[ 6. 10. 12.]
```
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