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from gffutils import iterators
from gffutils import interface
from collections import Counter
import sys
def inspect(data, look_for=['featuretype', 'chrom', 'attribute_keys',
'feature_count'], limit=None, verbose=True):
"""
Inspect a GFF or GTF data source.
This function is useful for figuring out the different featuretypes found
in a file (for potential removal before creating a FeatureDB).
Returns a dictionary with a key for each item in `look_for` and
a corresponding value that is a dictionary of how many of each unique item
were found.
There will always be a `feature_count` key, indicating how many features
were looked at (if `limit` is provided, then `feature_count` will be the
same as `limit`).
For example, if `look_for` is ['chrom', 'featuretype'], then the result
will be a dictionary like::
{
'chrom': {
'chr1': 500,
'chr2': 435,
'chr3': 200,
...
...
}.
'featuretype': {
'gene': 150,
'exon': 324,
...
},
'feature_count': 5000
}
Parameters
----------
data : str, FeatureDB instance, or iterator of Features
If `data` is a string, assume it's a GFF or GTF filename. If it's
a FeatureDB instance, then its `all_features()` method will be
automatically called. Otherwise, assume it's an iterable of Feature
objects.
look_for : list
List of things to keep track of. Options are:
- any attribute of a Feature object, such as chrom, source, start,
stop, strand.
- "attribute_keys", which will look at all the individual
attribute keys of each feature
limit : int
Number of features to look at. Default is no limit.
verbose : bool
Report how many features have been processed.
Returns
-------
dict
"""
results = {}
obj_attrs = []
for i in look_for:
if i not in ['attribute_keys', 'feature_count']:
obj_attrs.append(i)
results[i] = Counter()
attr_keys = 'attribute_keys' in look_for
d = iterators.DataIterator(data)
feature_count = 0
for f in d:
if verbose:
sys.stderr.write('\r%s features inspected' % feature_count)
sys.stderr.flush()
for obj_attr in obj_attrs:
results[obj_attr].update([getattr(f, obj_attr)])
if attr_keys:
results['attribute_keys'].update(f.attributes.keys())
feature_count += 1
if limit and feature_count == limit:
break
new_results = {}
for k, v in results.items():
new_results[k] = dict(v)
new_results['feature_count'] = feature_count
return new_results
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