pytutorial/glob/README.md

# [glob](https://docs.python.org/3/library/glob.html) : Finding files in a directory

## Goal
We want to deal with many files in a directory. What is an easy way to get the filename in a directory?

Questions to [David Rotermund](mailto:davrot@uni-bremen.de)

## Creating test files

```python
from pathlib import Path

Path("Testfile_1.mat").touch()
Path("Testfile_2.mat").touch()
Path("Testfile_10.mat").touch()
Path("Testfile_3.mat").touch()
```

## Using glob in a for-loop

```python
import glob

for filename in glob.glob("*.mat"):
    print(filename)
```

```python console
Testfile_1.mat
Testfile_2.mat
Testfile_10.mat
Testfile_3.mat
```

## Using glob to create a list

```python
import glob

list = glob.glob("*.mat")
print(list)
```

```python console
['Testfile_1.mat', 'Testfile_2.mat', 'Testfile_10.mat', 'Testfile_3.mat']
```

### Sorting the filenames

```python
import glob

list = sorted(glob.glob("*.mat"))
print(list)
```

```python console
['Testfile_1.mat', 'Testfile_10.mat', 'Testfile_2.mat', 'Testfile_3.mat']
```
Hmmm... This result is not helpful.

### Sorting the filenames with [natsort](https://pypi.org/project/natsort/)

```shell
pip install natsort
```

```python
import glob
from natsort import natsorted

list = natsorted(glob.glob("*.mat"))
print(list)
```

```python console
['Testfile_1.mat', 'Testfile_2.mat', 'Testfile_3.mat', 'Testfile_10.mat']
```

## rsplit 

And maybe you don't want to have the file extensions. Then we can use [rsplit](https://docs.python.org/3/library/stdtypes.html#str.rsplit) on the string.

```python
import glob
from natsort import natsorted

for filename in natsorted(glob.glob("*.mat")):
    print(filename.rsplit(".", 1)[0])
```

```python console
Testfile_1
Testfile_2
Testfile_3
Testfile_10
```

Alternatively without a for-loop but using [map](https://docs.python.org/3/library/functions.html#map) ,  [list](https://docs.python.org/3/library/functions.html#func-list) and [lambda functions](https://docs.python.org/3/reference/expressions.html#lambda):

```python
import glob
from natsort import natsorted

filenames = natsorted(glob.glob("*.mat"))
filenames = list(map(lambda s: s.rsplit(".", 1)[0], filenames))
print(filenames)
```

```python console
['Testfile_1', 'Testfile_2', 'Testfile_3', 'Testfile_10']
```