### pdbrow - select a subset of rows based on a filter

`pdbrow` can apply an arbitrary logical python expression that selects
matching rows for passing to the output.

#### Example input (*myfile.fsdb*):

```
#fsdb -F s col1:l two:a andthree:d
1	key1	42.0
2	key2	123.0
3	key1    90.2
```

#### Example command usage

```
$ pdbrow 'col1 == "key1"' myfile.fsdb
```

#### Example output

```
#fsdb -F t col1:l two andthree:d
1	key1	42.0
3	key1	90.2
#   | pdbrow 'two == "key1"' myfile.fsdb
```

#### Example command usage with initialization code


```
$ pdbrow -i "import re" 're.match("key1", two)' myfile.fsdb
```

#### Example output

```
#fsdb -F t col1:l two andthree:d
1	key1	42.0
3	key1	90.2
#   | pdbrow -i 'import re' 're.match("key1", two)' myfile.fsdb
```

#### Example command usage with namedtuple based rows

```
$ pdbrow -n row 'row.two == "key1"' myfile.fsdb
```

#### Example output

```
#fsdb -F t col1:l two andthree:d
1	key1	42.0
3	key1	90.2
#   | pdbrow -n row row.two == "key1"
```