Added CSV parsing to the tf.data programmers guide

Relevant to #278.

PiperOrigin-RevId: 197053723

diff --git a/tensorflow/docs_src/programmers_guide/datasets.md b/tensorflow/docs_src/programmers_guide/datasets.md
index 67be41b..8b69860 100644 (file)
--- a/tensorflow/docs_src/programmers_guide/datasets.md
+++ b/tensorflow/docs_src/programmers_guide/datasets.md
@@ -485,6 +485,46 @@ dataset = dataset.flat_map(
         .filter(lambda line: tf.not_equal(tf.substr(line, 0, 1), "#"))))
 ```
 
+### Consuming CSV data
+
+The CSV file format is a popular format for storing tabular data in plain text.
+The @{tf.contrib.data.CsvDataset} class provides a way to extract records from
+one or more CSV files that comply with [RFC 4180](https://tools.ietf.org/html/rfc4180).
+Given one or more filenames and a list of defaults, a `CsvDataset` will produce
+a tuple of elements whose types correspond to the types of the defaults
+provided, per CSV record. Like `TFRecordDataset` and `TextLineDataset`,
+`CsvDataset` accepts `filenames` as a `tf.Tensor`, so you can parameterize it
+by passing a  `tf.placeholder(tf.string)`.
+
+```
+# Creates a dataset that reads all of the records from two CSV files, each with
+# eight float columns
+filenames = ["/var/data/file1.csv", "/var/data/file2.csv"]
+record_defaults = [tf.float32] * 8   # Eight required float columns
+dataset = tf.contrib.data.CsvDataset(filenames, record_defaults)
+```
+
+If some columns are empty, you can provide defaults instead of types.
+
+```
+# Creates a dataset that reads all of the records from two CSV files, each with
+# four float columns which may have missing values
+record_defaults = [[0.0]] * 8
+dataset = tf.contrib.data.CsvDataset(filenames, record_defaults)
+```
+
+By default, a `CsvDataset` yields *every* column of *every* line of the file,
+which may not be desirable, for example if the file starts with a header line
+that should be ignored, or if some columns are not required in the input.
+These lines and fields can be removed with the `header` and `select_cols`
+arguments respectively.
+
+```
+# Creates a dataset that reads all of the records from two CSV files with
+# headers, extracting float data from columns 2 and 4.
+record_defaults = [[0.0]] * 2  # Only provide defaults for the selected columns
+dataset = tf.contrib.data.CsvDataset(filenames, record_defaults, header=True, select_cols=[2,4])
+```
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