# Editing a Package

Data in Quilt is organized in terms of **data packages**. A data package is a logical group of files, directories, and metadata.

### Initializing a package

To edit a new empty package, use the package constructor:

```python
import quilt3
p = quilt3.Package()
```

To edit a preexisting package, we need to first make sure to install the package:

```python
import quilt3
quilt3.Package.install(
    "examples/hurdat",
    "s3://quilt-example",
)
```

```
Loading manifest: 100%|██████████| 5/5 [00:00<00:00, 5902.48entries/s]

Successfully installed package 'examples/hurdat', tophash=f8d1478 from s3://quilt-example

```

Use `browse` to edit the package:

```python
p = quilt3.Package.browse('examples/hurdat')
```

```
Loading manifest: 100%|██████████| 5/5 [00:00<00:00, 9920.30entries/s]
```

For more information on accessing existing packages see the section "[Installing a Package](https://docs.quilt.bio/quilt-python-sdk/installing-a-package)".

### Adding data to a package

Use the `set` and `set_dir` commands to add individual files and whole directories, respectively, to a `Package`:

```python
# Create test directories
import quilt3
from pathlib import Path
from os import chdir
TEST_DIR = "test_workflow"
SUB_DIR = "subdir"

# create test directories
Path(TEST_DIR).mkdir(exist_ok=True)
Path(TEST_DIR, SUB_DIR).mkdir(exist_ok=True)
chdir(TEST_DIR) # %cd TEST_DIR/ if in Jupyter

# add entries individually using `set`
# ie p.set("foo.csv", "/local/path/foo.csv"),
# p.set("bar.csv", "s3://bucket/path/bar.csv")

# create test data
with open("data.csv", "w") as f:
    f.write("id, value\na, 42")

p = quilt3.Package()
p.set("data.csv", "data.csv")
p.set("banner.png", "s3://quilt-example/imgs/banner.png")

# or grab everything in a directory at once using `set_dir`
# ie p.set_dir("stuff/", "/path/to/stuff/"),
# p.set_dir("things/", "s3://path/to/things/")

# create logical directory in package
p.set_dir("stuff/", SUB_DIR)
p.set_dir("imgs/", "s3://quilt-example/imgs/")
```

```
(remote Package)
 └─banner.png
 └─data.csv
 └─imgs/
   └─banner.png
 └─stuff/
```

The first parameter to these functions is the *logical key*, which will determine where the file lives within the package. So after running the commands above our package will look like this:

```python
p
```

```
(remote Package)
 └─banner.png
 └─data.csv
 └─imgs/
   └─banner.png
 └─stuff/
```

The second parameter is the *physical key*, which states the file's actual location. The physical key may point to either a local file or a remote object (with an `s3://` path).

If the physical key and the logical key are the same, you may omit the second argument:

```python
import quilt3
p = quilt3.Package()
p.set("data.csv")
```

```
(local Package)
 └─data.csv
```

Another useful trick. Use `"."` to set the contents of the package to that of the current directory:

```python
# create a test file in test directory
with open("new_data.csv", "w") as f:
    f.write("id, value\na, 42")

# set the contents of the package to that of the current directory
p.set_dir(".", ".")
```

```
(local Package)
 └─data.csv
 └─new_data.csv
```

### Deleting data in a package

Use `delete` to remove entries from a package:

```python
p.delete("data.csv")
```

```
(local Package)
 └─new_data.csv
```

Note that this will only remove this piece of data from the package. It will not delete the actual data itself.

### Adding metadata to a package

Packages support metadata anywhere in the package. To set metadata on package entries or directories, use the `meta` argument:

```python
import quilt3
p = quilt3.Package()
p.set("data.csv", "new_data.csv", meta={"type": "csv"})
p.set_dir("subdir/", "subdir/", meta={"origin": "unknown"})
```

```
(local Package)
 └─data.csv
 └─subdir/
```

You can also set metadata on the package as a whole using `set_meta`.

```python
# set metadata on a package
p.set_meta({"package-type": "demo"})
```

```
(local Package)
 └─data.csv
 └─subdir/
```