1:mod:`!pprint` --- Data pretty printer 2====================================== 3 4.. module:: pprint 5 :synopsis: Data pretty printer. 6 7.. moduleauthor:: Fred L. Drake, Jr. <fdrake@acm.org> 8.. sectionauthor:: Fred L. Drake, Jr. <fdrake@acm.org> 9 10**Source code:** :source:`Lib/pprint.py` 11 12-------------- 13 14The :mod:`pprint` module provides a capability to "pretty-print" arbitrary 15Python data structures in a form which can be used as input to the interpreter. 16If the formatted structures include objects which are not fundamental Python 17types, the representation may not be loadable. This may be the case if objects 18such as files, sockets or classes are included, as well as many other 19objects which are not representable as Python literals. 20 21The formatted representation keeps objects on a single line if it can, and 22breaks them onto multiple lines if they don't fit within the allowed width, 23adjustable by the *width* parameter defaulting to 80 characters. 24 25Dictionaries are sorted by key before the display is computed. 26 27.. versionchanged:: 3.9 28 Added support for pretty-printing :class:`types.SimpleNamespace`. 29 30.. versionchanged:: 3.10 31 Added support for pretty-printing :class:`dataclasses.dataclass`. 32 33.. _pprint-functions: 34 35Functions 36--------- 37 38.. function:: pp(object, stream=None, indent=1, width=80, depth=None, *, \ 39 compact=False, sort_dicts=False, underscore_numbers=False) 40 41 Prints the formatted representation of *object*, followed by a newline. 42 This function may be used in the interactive interpreter 43 instead of the :func:`print` function for inspecting values. 44 Tip: you can reassign ``print = pprint.pp`` for use within a scope. 45 46 :param object: 47 The object to be printed. 48 49 :param stream: 50 A file-like object to which the output will be written 51 by calling its :meth:`!write` method. 52 If ``None`` (the default), :data:`sys.stdout` is used. 53 :type stream: :term:`file-like object` | None 54 55 :param int indent: 56 The amount of indentation added for each nesting level. 57 58 :param int width: 59 The desired maximum number of characters per line in the output. 60 If a structure cannot be formatted within the width constraint, 61 a best effort will be made. 62 63 :param depth: 64 The number of nesting levels which may be printed. 65 If the data structure being printed is too deep, 66 the next contained level is replaced by ``...``. 67 If ``None`` (the default), there is no constraint 68 on the depth of the objects being formatted. 69 :type depth: int | None 70 71 :param bool compact: 72 Control the way long :term:`sequences <sequence>` are formatted. 73 If ``False`` (the default), 74 each item of a sequence will be formatted on a separate line, 75 otherwise as many items as will fit within the *width* 76 will be formatted on each output line. 77 78 :param bool sort_dicts: 79 If ``True``, dictionaries will be formatted with 80 their keys sorted, otherwise 81 they will be displayed in insertion order (the default). 82 83 :param bool underscore_numbers: 84 If ``True``, 85 integers will be formatted with the ``_`` character for a thousands separator, 86 otherwise underscores are not displayed (the default). 87 88 >>> import pprint 89 >>> stuff = ['spam', 'eggs', 'lumberjack', 'knights', 'ni'] 90 >>> stuff.insert(0, stuff) 91 >>> pprint.pp(stuff) 92 [<Recursion on list with id=...>, 93 'spam', 94 'eggs', 95 'lumberjack', 96 'knights', 97 'ni'] 98 99 .. versionadded:: 3.8 100 101 102.. function:: pprint(object, stream=None, indent=1, width=80, depth=None, *, \ 103 compact=False, sort_dicts=True, underscore_numbers=False) 104 105 Alias for :func:`~pprint.pp` with *sort_dicts* set to ``True`` by default, 106 which would automatically sort the dictionaries' keys, 107 you might want to use :func:`~pprint.pp` instead where it is ``False`` by default. 108 109 110.. function:: pformat(object, indent=1, width=80, depth=None, *, \ 111 compact=False, sort_dicts=True, underscore_numbers=False) 112 113 Return the formatted representation of *object* as a string. *indent*, 114 *width*, *depth*, *compact*, *sort_dicts* and *underscore_numbers* are 115 passed to the :class:`PrettyPrinter` constructor as formatting parameters 116 and their meanings are as described in the documentation above. 117 118 119.. function:: isreadable(object) 120 121 .. index:: pair: built-in function; eval 122 123 Determine if the formatted representation of *object* is "readable", or can be 124 used to reconstruct the value using :func:`eval`. This always returns ``False`` 125 for recursive objects. 126 127 >>> pprint.isreadable(stuff) 128 False 129 130 131.. function:: isrecursive(object) 132 133 Determine if *object* requires a recursive representation. This function is 134 subject to the same limitations as noted in :func:`saferepr` below and may raise an 135 :exc:`RecursionError` if it fails to detect a recursive object. 136 137 138.. function:: saferepr(object) 139 140 Return a string representation of *object*, protected against recursion in 141 some common data structures, namely instances of :class:`dict`, :class:`list` 142 and :class:`tuple` or subclasses whose ``__repr__`` has not been overridden. If the 143 representation of object exposes a recursive entry, the recursive reference 144 will be represented as ``<Recursion on typename with id=number>``. The 145 representation is not otherwise formatted. 146 147 >>> pprint.saferepr(stuff) 148 "[<Recursion on list with id=...>, 'spam', 'eggs', 'lumberjack', 'knights', 'ni']" 149 150.. _prettyprinter-objects: 151 152PrettyPrinter Objects 153--------------------- 154 155.. index:: single: ...; placeholder 156 157.. class:: PrettyPrinter(indent=1, width=80, depth=None, stream=None, *, \ 158 compact=False, sort_dicts=True, underscore_numbers=False) 159 160 Construct a :class:`PrettyPrinter` instance. 161 162 Arguments have the same meaning as for :func:`~pprint.pp`. 163 Note that they are in a different order, and that *sort_dicts* defaults to ``True``. 164 165 >>> import pprint 166 >>> stuff = ['spam', 'eggs', 'lumberjack', 'knights', 'ni'] 167 >>> stuff.insert(0, stuff[:]) 168 >>> pp = pprint.PrettyPrinter(indent=4) 169 >>> pp.pprint(stuff) 170 [ ['spam', 'eggs', 'lumberjack', 'knights', 'ni'], 171 'spam', 172 'eggs', 173 'lumberjack', 174 'knights', 175 'ni'] 176 >>> pp = pprint.PrettyPrinter(width=41, compact=True) 177 >>> pp.pprint(stuff) 178 [['spam', 'eggs', 'lumberjack', 179 'knights', 'ni'], 180 'spam', 'eggs', 'lumberjack', 'knights', 181 'ni'] 182 >>> tup = ('spam', ('eggs', ('lumberjack', ('knights', ('ni', ('dead', 183 ... ('parrot', ('fresh fruit',)))))))) 184 >>> pp = pprint.PrettyPrinter(depth=6) 185 >>> pp.pprint(tup) 186 ('spam', ('eggs', ('lumberjack', ('knights', ('ni', ('dead', (...))))))) 187 188 189 .. versionchanged:: 3.4 190 Added the *compact* parameter. 191 192 .. versionchanged:: 3.8 193 Added the *sort_dicts* parameter. 194 195 .. versionchanged:: 3.10 196 Added the *underscore_numbers* parameter. 197 198 .. versionchanged:: 3.11 199 No longer attempts to write to :data:`!sys.stdout` if it is ``None``. 200 201 202:class:`PrettyPrinter` instances have the following methods: 203 204 205.. method:: PrettyPrinter.pformat(object) 206 207 Return the formatted representation of *object*. This takes into account the 208 options passed to the :class:`PrettyPrinter` constructor. 209 210 211.. method:: PrettyPrinter.pprint(object) 212 213 Print the formatted representation of *object* on the configured stream, 214 followed by a newline. 215 216The following methods provide the implementations for the corresponding 217functions of the same names. Using these methods on an instance is slightly 218more efficient since new :class:`PrettyPrinter` objects don't need to be 219created. 220 221 222.. method:: PrettyPrinter.isreadable(object) 223 224 .. index:: pair: built-in function; eval 225 226 Determine if the formatted representation of the object is "readable," or can be 227 used to reconstruct the value using :func:`eval`. Note that this returns 228 ``False`` for recursive objects. If the *depth* parameter of the 229 :class:`PrettyPrinter` is set and the object is deeper than allowed, this 230 returns ``False``. 231 232 233.. method:: PrettyPrinter.isrecursive(object) 234 235 Determine if the object requires a recursive representation. 236 237This method is provided as a hook to allow subclasses to modify the way objects 238are converted to strings. The default implementation uses the internals of the 239:func:`saferepr` implementation. 240 241 242.. method:: PrettyPrinter.format(object, context, maxlevels, level) 243 244 Returns three values: the formatted version of *object* as a string, a flag 245 indicating whether the result is readable, and a flag indicating whether 246 recursion was detected. The first argument is the object to be presented. The 247 second is a dictionary which contains the :func:`id` of objects that are part of 248 the current presentation context (direct and indirect containers for *object* 249 that are affecting the presentation) as the keys; if an object needs to be 250 presented which is already represented in *context*, the third return value 251 should be ``True``. Recursive calls to the :meth:`.format` method should add 252 additional entries for containers to this dictionary. The third argument, 253 *maxlevels*, gives the requested limit to recursion; this will be ``0`` if there 254 is no requested limit. This argument should be passed unmodified to recursive 255 calls. The fourth argument, *level*, gives the current level; recursive calls 256 should be passed a value less than that of the current call. 257 258 259.. _pprint-example: 260 261Example 262------- 263 264To demonstrate several uses of the :func:`~pprint.pp` function and its parameters, 265let's fetch information about a project from `PyPI <https://pypi.org>`_:: 266 267 >>> import json 268 >>> import pprint 269 >>> from urllib.request import urlopen 270 >>> with urlopen('https://pypi.org/pypi/sampleproject/1.2.0/json') as resp: 271 ... project_info = json.load(resp)['info'] 272 273In its basic form, :func:`~pprint.pp` shows the whole object:: 274 275 >>> pprint.pp(project_info) 276 {'author': 'The Python Packaging Authority', 277 'author_email': 'pypa-dev@googlegroups.com', 278 'bugtrack_url': None, 279 'classifiers': ['Development Status :: 3 - Alpha', 280 'Intended Audience :: Developers', 281 'License :: OSI Approved :: MIT License', 282 'Programming Language :: Python :: 2', 283 'Programming Language :: Python :: 2.6', 284 'Programming Language :: Python :: 2.7', 285 'Programming Language :: Python :: 3', 286 'Programming Language :: Python :: 3.2', 287 'Programming Language :: Python :: 3.3', 288 'Programming Language :: Python :: 3.4', 289 'Topic :: Software Development :: Build Tools'], 290 'description': 'A sample Python project\n' 291 '=======================\n' 292 '\n' 293 'This is the description file for the project.\n' 294 '\n' 295 'The file should use UTF-8 encoding and be written using ' 296 'ReStructured Text. It\n' 297 'will be used to generate the project webpage on PyPI, and ' 298 'should be written for\n' 299 'that purpose.\n' 300 '\n' 301 'Typical contents for this file would include an overview of ' 302 'the project, basic\n' 303 'usage examples, etc. Generally, including the project ' 304 'changelog in here is not\n' 305 'a good idea, although a simple "What\'s New" section for the ' 306 'most recent version\n' 307 'may be appropriate.', 308 'description_content_type': None, 309 'docs_url': None, 310 'download_url': 'UNKNOWN', 311 'downloads': {'last_day': -1, 'last_month': -1, 'last_week': -1}, 312 'home_page': 'https://github.com/pypa/sampleproject', 313 'keywords': 'sample setuptools development', 314 'license': 'MIT', 315 'maintainer': None, 316 'maintainer_email': None, 317 'name': 'sampleproject', 318 'package_url': 'https://pypi.org/project/sampleproject/', 319 'platform': 'UNKNOWN', 320 'project_url': 'https://pypi.org/project/sampleproject/', 321 'project_urls': {'Download': 'UNKNOWN', 322 'Homepage': 'https://github.com/pypa/sampleproject'}, 323 'release_url': 'https://pypi.org/project/sampleproject/1.2.0/', 324 'requires_dist': None, 325 'requires_python': None, 326 'summary': 'A sample Python project', 327 'version': '1.2.0'} 328 329The result can be limited to a certain *depth* (ellipsis is used for deeper 330contents):: 331 332 >>> pprint.pp(project_info, depth=1) 333 {'author': 'The Python Packaging Authority', 334 'author_email': 'pypa-dev@googlegroups.com', 335 'bugtrack_url': None, 336 'classifiers': [...], 337 'description': 'A sample Python project\n' 338 '=======================\n' 339 '\n' 340 'This is the description file for the project.\n' 341 '\n' 342 'The file should use UTF-8 encoding and be written using ' 343 'ReStructured Text. It\n' 344 'will be used to generate the project webpage on PyPI, and ' 345 'should be written for\n' 346 'that purpose.\n' 347 '\n' 348 'Typical contents for this file would include an overview of ' 349 'the project, basic\n' 350 'usage examples, etc. Generally, including the project ' 351 'changelog in here is not\n' 352 'a good idea, although a simple "What\'s New" section for the ' 353 'most recent version\n' 354 'may be appropriate.', 355 'description_content_type': None, 356 'docs_url': None, 357 'download_url': 'UNKNOWN', 358 'downloads': {...}, 359 'home_page': 'https://github.com/pypa/sampleproject', 360 'keywords': 'sample setuptools development', 361 'license': 'MIT', 362 'maintainer': None, 363 'maintainer_email': None, 364 'name': 'sampleproject', 365 'package_url': 'https://pypi.org/project/sampleproject/', 366 'platform': 'UNKNOWN', 367 'project_url': 'https://pypi.org/project/sampleproject/', 368 'project_urls': {...}, 369 'release_url': 'https://pypi.org/project/sampleproject/1.2.0/', 370 'requires_dist': None, 371 'requires_python': None, 372 'summary': 'A sample Python project', 373 'version': '1.2.0'} 374 375Additionally, maximum character *width* can be suggested. If a long object 376cannot be split, the specified width will be exceeded:: 377 378 >>> pprint.pp(project_info, depth=1, width=60) 379 {'author': 'The Python Packaging Authority', 380 'author_email': 'pypa-dev@googlegroups.com', 381 'bugtrack_url': None, 382 'classifiers': [...], 383 'description': 'A sample Python project\n' 384 '=======================\n' 385 '\n' 386 'This is the description file for the ' 387 'project.\n' 388 '\n' 389 'The file should use UTF-8 encoding and be ' 390 'written using ReStructured Text. It\n' 391 'will be used to generate the project ' 392 'webpage on PyPI, and should be written ' 393 'for\n' 394 'that purpose.\n' 395 '\n' 396 'Typical contents for this file would ' 397 'include an overview of the project, ' 398 'basic\n' 399 'usage examples, etc. Generally, including ' 400 'the project changelog in here is not\n' 401 'a good idea, although a simple "What\'s ' 402 'New" section for the most recent version\n' 403 'may be appropriate.', 404 'description_content_type': None, 405 'docs_url': None, 406 'download_url': 'UNKNOWN', 407 'downloads': {...}, 408 'home_page': 'https://github.com/pypa/sampleproject', 409 'keywords': 'sample setuptools development', 410 'license': 'MIT', 411 'maintainer': None, 412 'maintainer_email': None, 413 'name': 'sampleproject', 414 'package_url': 'https://pypi.org/project/sampleproject/', 415 'platform': 'UNKNOWN', 416 'project_url': 'https://pypi.org/project/sampleproject/', 417 'project_urls': {...}, 418 'release_url': 'https://pypi.org/project/sampleproject/1.2.0/', 419 'requires_dist': None, 420 'requires_python': None, 421 'summary': 'A sample Python project', 422 'version': '1.2.0'} 423