Printing unified output

For unified output of Katello CLI we use an instance of a printer class. Printer makes a common interface that supports multiple formatting strategies. Currently a verbose strategy and a grep friendly strategy is implemented. The first is by default used to display single dictionaries while the latter is used to print lists of dictionaries.

Before the records are printed it is necessary to restrict what columns will go to the output. This is done by function add_column which allows to set various column parameters.

Printer offers following methods (only the public ones listed):

Printer

class katello.client.utils.printer.Printer(strategy=None)

Unified interface for printing data in CLI.

add_column(attr_name, name=None, **kwargs)

Add column of data thet will be displayed

Parameters:

• attr_name (string) – key to data hash
• name (string) – label for the column. It is generated automatically from attr_name if it’s not set.
• kwargs (dict) – other parameters that are passed to the printer strategy

print_item(item)

Print one record

Parameters:item (dict) – data to be printed

print_items(items)

Print list of records

Parameters:items (list of dicts) – data to be printed

set_header(heading)

Sets label for a fancy header that is printed above the data.

Parameters:heading (string) –

set_strategy(strategy)

Sets formatting strategy

Parameters:strategy (PrinterStrategy) – strategy that is used for formatting the output.

Print strategies

Printer strategies have to implement methods print_item and print_items that take care of printing a single record or a list of them. They both take heading label, definition of columns (list of dictionaries) and the data.

Two strategies are used in CLI:

• VerboseStrategy - prints each column on a single line
• GrepStrategy - prints the data in a grid, one record per line

class katello.client.utils.printer.PrinterStrategy

Strategy of formatting the data and printing them on the output.

print_item(heading, columns, item)

Print one item

Parameters:

• heading (string) – Title for the list of items
• columns (list of dicts) – definition of columns
• item (dict) – data to be printed, one item

print_items(heading, columns, items)

Print list of items

Parameters:

• heading (string) – Title for the list of items
• columns (list of dicts) – definition of columns
• items (list of dicts) – data to be printed, list of items

Column Parameters Both print strategies support following column parameters:

Name	Type	Description
attr_name	string	Mandatory param, key to the data dictionary.
name	string	Label for the column. By default it is generated from the attr_name. Eg. “product_id” is translated to “Product Id”.
multiline	bool	Flag to mark values that can possibly hold strings with more lines. Strategies can handle them differently then.
formatter	function	A filter function for pre-formatting of values. Must take only one parameter which is the value that should be formatted. It is expected to return a string.
item_formatter	function	A filter function simmilar to formatter. The difference is in the parameter. This one takes the whole data dictionary. But still it must return single string.
value	string	Can be used to force static value.
show_with	strategy or a tuple of strategies	Allows to restrict what strategies the column can be printed with.

VerboseStrategy

class katello.client.utils.printer.VerboseStrategy

GrepStrategy

class katello.client.utils.printer.GrepStrategy(delimiter=None)

Prints data into a grid that can be grepped easily. String to divide the columns can be set optionally.

Usage example

from katello.client.utils.printer import Printer, VerboseStrategy, GrepStrategy

repo = get_repo() #returns a dictionary with repo data
# {
#   "id": 1,
#   "pulp_id": "ACME_Corporation-zoo-zoo",
#   "name": "zoo",
#   "package_count": 32,
#   "url": "http://tstrachota.fedorapeople.org/dummy_repos/zoo/",
#   "last_sync": "2012-04-16T00:27:37+02:00",
#   "sync_state": "finished"
# }

printer = Printer()
printer.set_strategy(VerboseStrategy()) # set a desired strategy
#printer.set_strategy(GrepStrategy(delimiter="|"))

printer.add_column('id') # 3 columns that only print the values
printer.add_column('name')
printer.add_column('package_count')
printer.add_column('url', show_with=VerboseStrategy) # this column will be printed only in the verbose mode
printer.add_column('last_sync', show_with=VerboseStrategy, formatter=format_sync_time) # only in verbose mode but preformatted by format_sync_time
printer.add_column('sync_state', name=_("Progress"), show_with=VerboseStrategy, formatter=format_sync_state) # same as above but with forced label

printer.set_header(_("Information About Repo %s") % repo['id'])

printer.print_item(repo)

Verbose strategy will print:

-------------------------------------------------------------------------------------------------
Information About Repo 1
-------------------------------------------------------------------------------------------------

Id:            1
Name:          zoo
Package Count: 32
Url:           http://tstrachota.fedorapeople.org/dummy_repos/zoo/
Last Sync:     2012/04/16 00:27:37
Progress:      Finished

With grep strategy it will print:

-------------------------------------------------------------------------------------------------
Information About Repo 1

| Id  | Name  | Package Count  |
-------------------------------------------------------------------------------------------------
| 1   | zoo   | 32             |