Input and Output (skbio.io)

This module provides input/output (I/O) functionality for scikit-bio.

Supported file formats

scikit-bio provides parsers for the following file formats. For details on what objects are supported by each format, see the associated documentation.

binary_dm	Simple binary dissimilarity matrix format (skbio.io.format.binary_dm)
biom	BIOM-Format (skbio.io.format.biom)
blast6	BLAST+6 format (skbio.io.format.blast6)
blast7	BLAST+7 format (skbio.io.format.blast7)
clustal	Clustal format (skbio.io.format.clustal)
embl	EMBL format (skbio.io.format.embl)
fasta	FASTA/QUAL format (skbio.io.format.fasta)
fastq	FASTQ format (skbio.io.format.fastq)
genbank	GenBank format (skbio.io.format.genbank)
gff3	GFF3 format (skbio.io.format.gff3)
lsmat	Labeled square matrix format (skbio.io.format.lsmat)
newick	Newick format (skbio.io.format.newick)
ordination	Ordination results format (skbio.io.format.ordination)
phylip	PHYLIP multiple sequence alignment format (skbio.io.format.phylip)
qseq	QSeq format (skbio.io.format.qseq)
stockholm	Stockholm format (skbio.io.format.stockholm)
taxdump	Taxdump format (skbio.io.format.taxdump)
sample_metadata	Sample Metadata object ported over from qiime2.

Read/write files

Generic I/O functions

write(self, obj, format, into, **kwargs)	Write an object as certain format into a file.
read(self, file[, format, into, verify])	Read a file as certain format into an object.
sniff(self, file, **kwargs)	Detect the format of a given file and suggest kwargs for reading.

Additional I/O utilities

util	I/O utilities (skbio.io.util)

Develop custom formats

Developer documentation on extending I/O

registry

I/O Registry (skbio.io.registry)

Exceptions and warnings

General exceptions and warnings

FormatIdentificationWarning	Warn when the sniffer of a format cannot confirm the format.
ArgumentOverrideWarning	Warn when a user provided kwarg differs from a guessed kwarg.
UnrecognizedFormatError	Raised when a file's format is unknown, ambiguous, or unidentifiable.
IOSourceError	Raised when a file source cannot be resolved.
FileFormatError	Raised when a file cannot be parsed.

Format-specific exceptions and warnings

BLAST7FormatError	Raised when a blast7 formatted file cannot be parsed.
ClustalFormatError	Raised when a clustal formatted file cannot be parsed.
EMBLFormatError	Raised when a EMBL formatted file cannot be parsed.
FASTAFormatError	Raised when a fasta formatted file cannot be parsed.
FASTQFormatError	Raised when a fastq formatted file cannot be parsed.
GenBankFormatError	Raised when a genbank formatted file cannot be parsed.
GFF3FormatError	Raised when a GFF3 formatted file cannot be parsed.
LSMatFormatError	Raised when a lsmat formatted file cannot be parsed.
NewickFormatError	Raised when a newick formatted file cannot be parsed.
OrdinationFormatError	Raised when an ordination formatted file cannot be parsed.
PhylipFormatError	Raised when a phylip formatted file cannot be parsed.
QSeqFormatError	Raised when a qseq formatted file cannot be parsed.
QUALFormatError	Raised when a qual formatted file cannot be parsed.
StockholmFormatError	Raised when a stockholm formatted file cannot be parsed.

Tutorial

Reading and writing files (I/O) can be a complicated task:

• A file format can sometimes be read into more than one in-memory representation (i.e., object). For example, a FASTA file can be read into an skbio.alignment.TabularMSA or skbio.sequence.DNA depending on what operations you’d like to perform on your data.

• A single object might be writeable to more than one file format. For example, an skbio.alignment.TabularMSA object could be written to FASTA, FASTQ, CLUSTAL, or PHYLIP formats, just to name a few.

• You might not know the exact file format of your file, but you want to read it into an appropriate object.

• You might want to read multiple files into a single object, or write an object to multiple files.

• Instead of reading a file into an object, you might want to stream the file using a generator (e.g., if the file cannot be fully loaded into memory).

To address these issues (and others), scikit-bio provides a simple, powerful interface for dealing with I/O. We accomplish this by using a single I/O registry.

What kinds of files scikit-bio can use

To see a complete list of file-like inputs that can be used for reading, writing, and sniffing, see the documentation for skbio.io.util.open().

Reading files into scikit-bio

There are two ways to read files. The first way is to use the procedural interface:

my_obj = skbio.io.read(file, format='someformat', into=SomeSkbioClass)

The second is to use the object-oriented (OO) interface which is automatically constructed from the procedural interface:

my_obj = SomeSkbioClass.read(file, format='someformat')

For example, to read a newick file using both interfaces you would type:

>>> from skbio import read
>>> from skbio import TreeNode
>>> from io import StringIO
>>> open_filehandle = StringIO('(a, b);')
>>> tree = read(open_filehandle, format='newick', into=TreeNode)
>>> tree
<TreeNode, name: unnamed, internal node count: 0, tips count: 2>

For the OO interface:

>>> open_filehandle = StringIO('(a, b);')
>>> tree = TreeNode.read(open_filehandle, format='newick')
>>> tree
<TreeNode, name: unnamed, internal node count: 0, tips count: 2>

In the case of skbio.io.registry.read() if into is not provided, then a generator will be returned. What the generator yields will depend on what format is being read.

When into is provided, format may be omitted and the registry will use its knowledge of the available formats for the requested class to infer the correct format. This format inference is also available in the OO interface, meaning that format may be omitted there as well.

As an example:

>>> open_filehandle = StringIO('(a, b);')
>>> tree = TreeNode.read(open_filehandle)
>>> tree
<TreeNode, name: unnamed, internal node count: 0, tips count: 2>

We call format inference sniffing, much like the csv.Sniffer class of Python’s standard library. The goal of a sniffer is two-fold: to identify if a file is a specific format, and if it is, to provide **kwargs which can be used to better parse the file.

Note

There is a built-in sniffer which results in a useful error message if an empty file is provided as input and the format was omitted.

Writing files from scikit-bio

Just as when reading files, there are two ways to write files.

Procedural Interface:

skbio.io.write(my_obj, format='someformat', into=file)

OO Interface:

my_obj.write(file, format='someformat')

In the procedural interface, format is required. Without it, scikit-bio does not know how you want to serialize an object. OO interfaces define a default format, so it may not be necessary to include it.