.. _module: .. py:module:: bitmath The ``bitmath`` Module ###################### .. contents:: :depth: 3 :local: Functions ********* This section describes utility functions included in the :py:mod:`bitmath` module. .. _bitmath_getsize: bitmath.getsize() ================= .. function:: getsize(path[, bestprefix=True[, system=NIST]]) Return a bitmath instance representing the size of a file at any given path. :param string path: The path of a file to read the size of :param bool bestprefix: **Default:** ``True``, the returned instance will be in the best human-readable prefix unit. If set to ``False`` the result is a ``bitmath.Byte`` instance. :param system: **Default:** :py:data:`bitmath.NIST`. The preferred system of units for the returned instance. :type system: One of :py:data:`bitmath.NIST` or :py:data:`bitmath.SI` Internally :py:func:`bitmath.getsize` calls :py:func:`os.path.realpath` before calling :py:func:`os.path.getsize` on any paths. Here's an example of where we'll run :py:func:`bitmath.getsize` on the bitmath source code using the defaults for the ``bestprefix`` and ``system`` parameters: .. code-block:: python >>> import bitmath >>> print bitmath.getsize('./bitmath/__init__.py') 33.3583984375 KiB Let's say we want to see the results in bytes. We can do this by setting ``bestprefix`` to ``False``: .. code-block:: python >>> import bitmath >>> print bitmath.getsize('./bitmath/__init__.py', bestprefix=False) 34159.0 Byte Recall, the default for representation is with the best human-readable prefix. We can control the prefix system used by setting ``system`` to either :py:data:`bitmath.NIST` (the default) or :py:data:`bitmath.SI`: .. code-block:: python :linenos: :emphasize-lines: 1-4 >>> print bitmath.getsize('./bitmath/__init__.py') 33.3583984375 KiB >>> print bitmath.getsize('./bitmath/__init__.py', system=bitmath.NIST) 33.3583984375 KiB >>> print bitmath.getsize('./bitmath/__init__.py', system=bitmath.SI) 34.159 kB We can see in lines **1** → **4** that the same result is returned when ``system`` is not set and when ``system`` is set to :py:data:`bitmath.NIST` (the default). .. versionadded:: 1.0.7 bitmath.listdir() ================= .. function:: listdir(search_base[, followlinks=False[, filter='*'[, relpath=False[, bestprefix=False[, system=NIST]]]]]) This is a `generator `_ which recurses a directory tree yielding 2-tuples of: * The absolute/relative path to a discovered file * A bitmath instance representing the *apparent size* of the file :param string search_base: The directory to begin walking down :param bool followlinks: **Default:** ``False``, do not follow links. Whether or not to follow symbolic links to directories. Setting to ``True`` enables directory link following :param string filter: **Default:** ``*`` (everything). A glob to filter results with. See `fnmatch `_ for more details about *globs* :param bool relpath: **Default:** ``False``, returns the fully qualified to each discovered file. ``True`` to return the relative path from the present working directory to the discovered file. If ``relpath`` is ``False``, then :py:func:`bitmath.listdir` internally calls :py:func:`os.path.realpath` to normalize path references :param bool bestprefix: **Default:** ``False``, returns ``bitmath.Byte`` instances. Set to ``True`` to return the best human-readable prefix unit for representation :param system: **Default:** :py:data:`bitmath.NIST`. Set a prefix preferred unit system. Requires ``bestprefix`` is ``True`` :type system: One of :py:data:`bitmath.NIST` or :py:data:`bitmath.SI` .. note:: * This function does **not** return tuples for directory entities. Including directories in results is `scheduled for introduction `_ in the upcoming 1.1.0 release. * Symlinks to **files** are followed automatically When interpreting the results from this function it is *crucial* to understand exactly which items are being taken into account, what decisions were made to select those items, and how their sizes are measured. Results from this function may seem invalid when directly compared to the results from common command line utilities, such as ``du``, or ``tree``. Let's pretend we have a directory structure like the following:: some_files/ ├── deeper_files/ │   └── second_file └── first_file Where ``some_files/`` is a directory, and so is ``some_files/deeper_files/``. There are two regular files in this tree: * ``somefiles/first_file`` - 1337 Bytes * ``some_files/deeper_files/second_file`` - 13370 Bytes The **total** size of the files in this tree is **1337 + 13370 = 14707** bytes. Let's call :py:func:`bitmath.listdir` on the ``some_files/`` directory and see what the results look like. First we'll use all the default parameters, then we'll set ``relpath`` to ``True``: .. code-block:: python :linenos: :emphasize-lines: 5-6,10-11 >>> import bitmath >>> for f in bitmath.listdir('./some_files'): ... print f ... ('/tmp/tmp.P5lqtyqwPh/some_files/first_file', Byte(1337.0)) ('/tmp/tmp.P5lqtyqwPh/some_files/deeper_files/second_file', Byte(13370.0)) >>> for f in bitmath.listdir('./some_files', relpath=True): ... print f ... ('some_files/first_file', Byte(1337.0)) ('some_files/deeper_files/second_file', Byte(13370.0)) On lines **5** and **6** the results print the full path, whereas on lines **10** and **11** the path is relative to the present working directory. Let's play with the ``filter`` parameter now. Let's say we only want to include results for files whose name begins with "second": .. code-block:: python >>> for f in bitmath.listdir('./some_files', filter='second*'): ... print f ... ('/tmp/tmp.P5lqtyqwPh/some_files/deeper_files/second_file', Byte(13370.0)) If we wish to avoid having to write for-loops, we can collect the results into a list rather simply: .. code-block:: python >>> files = list(bitmath.listdir('./some_files')) >>> print files [('/tmp/tmp.P5lqtyqwPh/some_files/first_file', Byte(1337.0)), ('/tmp/tmp.P5lqtyqwPh/some_files/deeper_files/second_file', Byte(13370.0))] Here's a more advanced example where we will sum the size of all the returned results and then play around with the possible formatting. Recall that a bitmath instance representing the size of the discovered file is the second item in each returned tuple. .. code-block:: python >>> discovered_files = [f[1] for f in bitmath.listdir('./some_files')] >>> print discovered_files [Byte(1337.0), Byte(13370.0)] >>> print reduce(lambda x,y: x+y, discovered_files) 14707.0 Byte >>> print reduce(lambda x,y: x+y, discovered_files).best_prefix() 14.3623046875 KiB >>> print reduce(lambda x,y: x+y, discovered_files).best_prefix().format("{value:.3f} {unit}") 14.362 KiB .. versionadded:: 1.0.7 bitmath.parse_string() ====================== .. function:: parse_string(str_repr) .. versionadded:: 1.1.0 Parse a string representing a unit into a proper bitmath object. All non-string inputs are rejected and will raise a :py:exc:`ValueError`. Strings without units are also rejected. See the examples below for additional clarity. :param string str_repr: The string to parse. May contain whitespace between the value and the unit. :return: A bitmath object representing ``str_repr`` :raises ValueError: if ``str_repr`` can not be parsed A simple usage example: .. code-block:: python >>> import bitmath >>> a_dvd = bitmath.parse_string("4.7 GiB") >>> print type(a_dvd) >>> print a_dvd 4.7 GiB .. caution:: Caution is advised if you are reading values from an unverified external source, such as output from a shell command or a generated file. Many applications (even ``/usr/bin/ls``) still do not produce file size strings with valid (or even correct) prefix units unless `specially configured to do so `_. To protect your application from unexpected runtime errors it is recommended that calls to :py:func:`bitmath.parse_string` are wrapped in a ``try`` statement: .. code-block:: python >>> import bitmath >>> try: ... a_dvd = bitmath.parse_string("4.7 G") ... except ValueError: ... print "Error while parsing string into bitmath object" ... Error while parsing string into bitmath object Here we can see some more examples of invalid input, as well as two acceptable inputs: .. code-block:: python >>> import bitmath >>> sizes = [ 1337, 1337.7, "1337", "1337.7", "1337 B", "1337B" ] >>> for size in sizes: ... try: ... print "Parsed size into %s" % bitmath.parse_string(size).best_prefix() ... except ValueError: ... print "Could not parse input: %s" % size ... Could not parse input: 1337 Could not parse input: 1337.7 Could not parse input: 1337 Could not parse input: 1337.7 Parsed size into 1.3056640625 KiB Parsed size into 1.3056640625 KiB .. versionchanged:: 1.2.4 Added support for parsing *octet* units via issue `#53 - parse french units `_. The `usage `_ of "octet" is still common in some `RFCs `_, as well as France, French Canada and Romania. See also, a table of the octet units and their values on `Wikipedia `_. Here are some simple examples of parsing *octet* based units: .. code-block:: python :linenos: :emphasize-lines: 4,5 >>> import bitmath >>> a_mebibyte = bitmath.parse_string("1 MiB") >>> a_mebioctet = bitmath.parse_string("1 Mio") >>> print a_mebibyte, a_mebioctet 1.0 MiB 1.0 MiB >>> print bitmath.parse_string("1Po") 1.0 PB >>> print bitmath.parse_string("1337 Eio") 1337.0 EiB Notice how on lines **4** and **5** that the variable ``a_mebibyte`` from the input ``1 MiB`` is exactly equivalent to ``a_mebioctet`` from the different input ``1 Mio``. This is because after :py:mod:`bitmath` parses the octet units the results are normalized into their **standard** NIST/SI equivalents automatically. bitmath.parse_string_unsafe() ============================= .. function:: parse_string_unsafe(repr) .. versionadded:: 1.3.1 Parse a string or number into a proper bitmath object. This is the less strict version of the :py:func:`bitmath.parse_string` function. While :py:func:`bitmath.parse_string` only accepts SI and NIST defined unit prefixes, :py:func:`bitmath.parse_string_unsafe` accepts *non-standard* units such as those often displayed in command-line output. :param repr: The value to parse. May contain whitespace between the value and the unit. :return: A bitmath object representing ``repr`` :raises ValueError: if ``repr`` can not be parsed Use of this function comes with several caveats: * All inputs are assumed to be byte-based (as opposed to bit based) * Numerical inputs (those without any units) are assumed to be a number of bytes * Inputs with single letter units (``k``, ``M``, ``G``, etc) are assumed to be SI units (base 10) * Inputs with an ``i`` character following the leading letter (``Ki``, ``Mi``, ``Gi``) are assumed to be NIST units (base 2) * Capitalization does not matter What exactly are these *non-standard* units? Generally speaking non-standard units will not include enough information to be able to identify exactly which unit system is being used. This is caused by mis-capitalized characters (capital ``k``'s for SI *kilo* units when they should be lower case), or omitted Byte or Bit suffixes. You can find examples of non-standard units in many common command line functions or parameters. For example: * The ``ls`` command will print out single-letter units when given the ``-h`` option flag * Running ``qemu-img info virtualdisk.img`` will also report with single letter units * The ``df`` command also uses single-letter units * `Kubernetes `_ will display items like *memory limits* using two letter NIST units (ex: ``memory: 2370Mi``) Given those considerations, understanding exactly what values you are feeding into this function is crucial to getting accurate results. You can control the output of some commands with various option flags. For example, you could ensure the GNU ``ls`` and ``df`` commands print with SI values by providing the ``--si`` option flag. By default those commands will print out using NIST (base 2) values. bitmath.query_device_capacity() =============================== .. function:: query_device_capacity(device_fd) Create :class:`bitmath.Byte` instances representing the capacity of a block device. :param file device_fd: An open file handle (``handle = open('/dev/sda')``) of the target device. :return: A :class:`bitmath.Byte` equal to the size of ``device_fd`` :raises ValueError: if file descriptor ``device_fd`` is not of a device type :raises IOError: * :py:exc:`IOError[13]` - If the effective **uid** of this process does not have access to issue raw commands to block devices. I.e., this process does not have super-user rights * :py:exc:`IOError[2]` - If the device ``device_fd`` points to does not exist .. include:: query_device_capacity_warning.rst .. include:: example_block_devices.rst Here's an example using the ``with`` context manager to open a device and print its capacity with the best-human readable prefix (line **3**): .. code-block:: python :linenos: :emphasize-lines: 3 >>> import bitmath >>> with open("/dev/sda") as device: ... size = bitmath.query_device_capacity(device).best_prefix() ... print "Device %s capacity: %s (%s Bytes)" % (device.name, size, size_bytes) Device /dev/sda capacity: 238.474937439 GiB (2.56060514304e+11 Bytes) .. important:: **Platform Notice**: :py:func:`bitmath.query_device_capacity` is only verified to work on **Linux** and **Mac OS X** platforms. To file a bug report, please follow the instructions in the :ref:`contributing section`. .. versionadded:: 1.2.4 .. _module_context_managers: Context Managers **************** This section describes all of the `context managers `_ provided by the bitmath class. .. note:: For a bit of background, a *context manager* (specifically, the ``with`` statement) is a feature of the Python language which is commonly used to: * Decorate, or *wrap*, an arbitrary block of code. I.e., effect a certain condition onto a specific body of code * Automatically *open* and *close* an object which is used in a specific context. I.e., handle set-up and tear-down of objects in the place they are used. .. seealso:: :pep:`343` *The "with" Statement* :pep:`318` *Decorators for Functions and Methods* .. _module_bitmath_format: bitmath.format() ================ .. function:: format([fmt_str=None[, plural=False[, bestprefix=False]]]) The :py:func:`bitmath.format` context manager allows you to specify the string representation of all bitmath instances within a specific block of code. This is effectively equivalent to applying the :ref:`format()` method to an entire region of code. :param str fmt_str: a formatting mini-language compat formatting string. See the :ref:`instance attributes ` for a list of available items. :param bool plural: ``True`` enables printing instances with trailing **s**'s if they're plural. ``False`` (default) prints them as singular (no trailing 's') :param bool bestprefix: ``True`` enables printing instances in their best human-readable representation. ``False``, the default, prints instances using their current prefix unit. .. note:: The ``bestprefix`` parameter is not yet implemented! Let's look at an example of toggling pluralization on and off. First we'll look over a demonstration script (below), and then we'll review the output. .. code-block:: python :linenos: :emphasize-lines: 33-34 import bitmath a_single_bit = bitmath.Bit(1) technically_plural_bytes = bitmath.Byte(0) always_plural_kbs = bitmath.kb(42) formatting_args = { 'not_plural': a_single_bit, 'technically_plural': technically_plural_bytes, 'always_plural': always_plural_kbs } print """None of the following will be pluralized, because that feature is turned off """ test_string = """ One unit of 'Bit': {not_plural} 0 of a unit is typically said pluralized in US English: {technically_plural} several items of a unit will always be pluralized in normal US English speech: {always_plural}""" print test_string.format(**formatting_args) print """ ---------------------------------------------------------------------- """ print """Now, we'll use the bitmath.format() context manager to print the same test string, but with pluralization enabled. """ with bitmath.format(plural=True): print test_string.format(**formatting_args) The context manager is demonstrated in lines **33** → **34**. In these lines we use the :py:func:`bitmath.format` context manager, setting ``plural`` to ``True``, to print the original string again. By doing this we have enabled pluralized string representations (where appropriate). Running this script would have the following output:: None of the following will be pluralized, because that feature is turned off One unit of 'Bit': 1.0 Bit 0 of a unit is typically said pluralized in US English: 0.0 Byte several items of a unit will always be pluralized in normal US English speech: 42.0 kb ---------------------------------------------------------------------- Now, we'll use the bitmath.format() context manager to print the same test string, but with pluralization enabled. One unit of 'Bit': 1.0 Bit 0 of a unit is typically said pluralized in US English: 0.0 Bytes several items of a unit will always be pluralized in normal US English speech: 42.0 kbs Here's a shorter example, where we'll: * Print a string containing bitmath instances using the default formatting (lines **2** → **3**) * Use the context manager to print the instances in scientific notation (lines **4** → **7**) * Print the string one last time to demonstrate how the formatting automatically returns to the default format (lines **8** → **9**) .. code-block:: python :linenos: >>> import bitmath >>> print "Some instances: %s, %s" % (bitmath.KiB(1 / 3.0), bitmath.Bit(512)) Some instances: 0.333333333333 KiB, 512.0 Bit >>> with bitmath.format("{value:e}-{unit}"): ... print "Some instances: %s, %s" % (bitmath.KiB(1 / 3.0), bitmath.Bit(512)) ... Some instances: 3.333333e-01-KiB, 5.120000e+02-Bit >>> print "Some instances: %s, %s" % (bitmath.KiB(1 / 3.0), bitmath.Bit(512)) Some instances: 0.333333333333 KiB, 512.0 Bit .. versionadded:: 1.0.8 .. _module_class_variables: Module Variables **************** This section describes the module-level variables. Some of which are constants and are used for reference. Some of which effect output or behavior. .. versionchanged:: 1.0.7 The formatting strings were not available for manupulate/inspection in earlier versions .. versionadded:: 1.1.1 Prior to this version :py:data:`ALL_UNIT_TYPES` was not defined .. note:: Modifying these variables will change the default representation indefinitely. Use the :py:func:`bitmath.format` context manager to limit changes to a specific block of code. .. _module_format_string: .. py:data:: format_string This is the default string representation of all bitmath instances. The default value is ``{value} {unit}`` which, when evaluated, formats an instance as a floating point number with at least one digit of precision, followed by a character of whitespace, followed by the prefix unit of the instance. For example, given bitmath instances representing the following values: **1337 MiB**, **0.1234567 kb**, and **0 B**, their printed output would look like the following: .. code-block:: python >>> from bitmath import * >>> print MiB(1337), kb(0.1234567), Byte(0) 1337.0 MiB 0.1234567 kb 0.0 Byte We can make these instances print however we want to. Let's wrap each one in square brackets (``[``, ``]``), replace the separating space character with a hyphen (``-``), and limit the precision to just 2 digits: .. code-block:: python >>> import bitmath >>> bitmath.format_string = "[{value:.2f}-{unit}]" >>> print bitmath.MiB(1337), bitmath.kb(0.1234567), bitmath.Byte(0) [1337.00-MiB] [0.12-kb] [0.00-Byte] .. py:data:: format_plural A boolean which controls the pluralization of instances in string representation. The default is ``False``. If we wanted to enable pluralization we could set the :py:data:`format_plural` variable to ``True``. First, let's look at some output using the default singular formatting. .. code-block:: python >>> import bitmath >>> print bitmath.MiB(1337) 1337.0 MiB And now we'll enable pluralization (line **2**): .. code-block:: python :linenos: :emphasize-lines: 2,5 >>> import bitmath >>> bitmath.format_plural = True >>> print bitmath.MiB(1337) 1337.0 MiBs >>> bitmath.format_plural = False >>> print bitmath.MiB(1337) 1337.0 MiB On line **5** we disable pluralization again and then see that the output has no trailing "s" character. .. py:data:: NIST Constant used as an argument to some functions to specify the **NIST** system. .. py:data:: SI Constant used as an argument to some functions to specify the **SI** system. .. py:data:: SI_PREFIXES An array of all of the SI unit prefixes (e.g., ``k``, ``M``, or ``E``) .. py:data:: SI_STEPS .. code-block:: python SI_STEPS = { 'Bit': 1 / 8.0, 'Byte': 1, 'k': 1000, 'M': 1000000, 'G': 1000000000, 'T': 1000000000000, 'P': 1000000000000000, 'E': 1000000000000000000 } .. py:data:: NIST_PREFIXES An array of all of the NIST unit prefixes (e.g., ``Ki``, ``Mi``, or ``Ei``) .. py:data:: NIST_STEPS .. code-block:: python NIST_STEPS = { 'Bit': 1 / 8.0, 'Byte': 1, 'Ki': 1024, 'Mi': 1048576, 'Gi': 1073741824, 'Ti': 1099511627776, 'Pi': 1125899906842624, 'Ei': 1152921504606846976 } .. py:data:: ALL_UNIT_TYPES An array of all combinations of known valid prefix units mixed with both bit and byte suffixes. .. code-block:: python ALL_UNIT_TYPES = ['b', 'B', 'kb', 'kB', 'Mb', 'MB', 'Gb', 'GB', 'Tb', 'TB', 'Pb', 'PB', 'Eb', 'EB', 'Kib', 'KiB', 'Mib', 'MiB', 'Gib', 'GiB', 'Tib', 'TiB', 'Pib', 'PiB', 'Eib', 'EiB'] .. py:module:: bitmath.integrations 3rd Party Module Integrations ***************************** This section describes the various ways in which :py:mod:`bitmath` can be integrated with other 3rd pary modules. To see a full demo of the :mod:`argparse` and :mod:`progressbar` integrations, as well as a comprehensive demonstrations of the full capabilities of the bitmath library, see :ref:`Creating Download Progress Bars ` in the *Real Life Examples* section. .. _bitmath_BitmathType: argparse ======== .. versionadded:: 1.2.0 The `argparse module `_ (part of stdlib) is used to parse command line arguments. By default, parsed options and arguments are turned into strings. However, one useful feature :py:mod:`argparse` provides is the ability to `specify what datatype `_ any given argument or option should be interpreted as. .. function:: BitmathType(bmstring) The :func:`BitmathType` factory creates objects that can be passed to the type argument of `ArgumentParser.add_argument() `_. Arguments that have :func:`BitmathType` objects as their type will automatically parse the command line argument into a matching :ref:`bitmath object `. :param str bmstring: The command-line option to parse into a bitmath object :returns: A bitmath object representing ``bmstring`` :raises ValueError: on any input that :py:func:`bitmath.parse_string` already rejects :raises ValueError: on **unquoted inputs** with whitespace separating the value from the unit (e.g., ``--some-option 10 MiB`` is bad, but ``--some-option '10 MiB'`` is good) Let's take a look at a more in-depth example. A feature found in many command-line utilities is the ability to specify some kind of file size using a string which roughly describes some kind of parameter. For example, let's look at the :program:`du` (disk usage) command. Invoking it as :option:`du -B` allows one to specify a desired block-size scaling factor in printed results. Let's say we wanted to implement a similar mechanism in an application of our own. Except, instead of abbreviating down to ambiguous capital letters, we accept scaling factors as :ref:`properly written values ` with associated units. Such as **10 MiB**, or **1 MB**. To accomplish this, we'll use :py:mod:`argparse` to create an argument parser and add one option to it, ``--block-size``. This option will have a type of :func:`BitmathType` set. .. code-block:: python :linenos: :emphasize-lines: 3,6,7 >>> import argparse, bitmath >>> parser = argparse.ArgumentParser() >>> parser.add_argument('--block-size', type=bitmath.BitmathType) >>> args = "--block-size 1MiB" >>> results = parser.parse_args(args.split()) >>> print type(results.block_size) On line **3** we add the ``--block-size`` option to the parser, explicitly defining it's type as :func:`BitmathType`. In lines **6** and **7** when we parse the provided arguments we find that :py:mod:`argparse` has automatically created a bitmath object for us. If an invalid scaling factor is provided by the user, such as one which does not represent a recognizable unit, the bitmath library will automatically detect this for us and signal to the argument parser that an error has occurred. .. _bitmath_BitmathFileTransferSpeed: progressbar =========== .. versionadded:: 1.2.1 The `progressbar module `_ is typically used to display the progress of a long running task, such as a file transfer operation. The module provides widgets for custom formatting how exactly the 'progress' is displayed. Some examples include: overall percentage complete, estimated time until completion, and an ASCII progress bar which fills as the operation continues. While :mod:`progressbar` already includes a widget suitable for displaying `file transfer rates `_, this widget does not support customizing its presentation, and is limited to only prefix units from the SI system. .. class:: BitmathFileTransferSpeed([system=bitmath.NIST, [format="{value:.2f} {unit}/s"]]) The :class:`BitmathFileTransferSpeed` class is a more functional replacement for the upstream `FileTransferSpeed `_ widget. While both widgets are able to calculate average transfer rates over a period of time, the :class:`BitmathFileTransferSpeed` widget adds new support for `NIST `_ prefix units (the upstream widget only supports SI prefix units). In addition to NIST unit support, :class:`BitmathFileTransferSpeed` enables the user to have **full control** over the look and feel of the displayed rates. :param system: **Default:** :py:data:`bitmath.NIST`. The preferred system of units for the printed rate. :type system: One of :py:data:`bitmath.NIST` or :py:data:`bitmath.SI` :param string format: a formatting mini-language compat formatting string. **Default** ``{value:.2f} {unit}/s`` (e.g., ``13.37 GiB/s``) .. note:: See :ref:`instance attributes ` for a list of available formatting items. See the section on :ref:`formatting bitmath instances ` for more information on this topic. Use :class:`BitmathFileTransferSpeed` exactly like the upstream ``FileTransferSpeed`` widget (example copied and modified from the progressbar project page): .. code-block:: python :linenos: :emphasize-lines: 2,4 >>> from progressbar import ProgressBar, Percentage, Bar, ETA, RotatingMarker >>> from bitmath.integrations import BitmathFileTransferSpeed >>> widgets = ['Something: ', Percentage(), ' ', Bar(marker=RotatingMarker()), ... ' ', ETA(), ' ', BitmathFileTransferSpeed()] >>> pbar = ProgressBar(widgets=widgets, maxval=10000000).start() >>> for i in range(1000000): ... # do something ... pbar.update(10*i+1) >>> pbar.finish() If this was ran from a script we would see output similar to the following:: Something: 100% ||||||||||||||||||||||||||||||||||| Time: 0:00:01 9.27 MiB/s If we wanted behavior identical to :class:`FileTransferSpeed` we would set the ``system`` parameter to :py:data:`bitmath.SI` (line **5** below): .. code-block:: python :linenos: :emphasize-lines: 5 >>> import bitmath >>> # ... >>> widgets = ['Something: ', Percentage(), ' ', Bar(marker=RotatingMarker()), ... ' ', ETA(), ' ', ... BitmathFileTransferSpeed(system=bitmath.SI)] >>> pbar = ProgressBar(widgets=widgets, maxval=10000000).start() >>> # ... If this was ran from a script we would see output similar to the following:: Something: 100% ||||||||||||||||||||||||||||||||||| Time: 0:00:01 9.80 MB/s Note how the only difference is in the displayed unit. The former example produced a rate with a unit of ``MiB`` (a NIST unit) whereas the latter examples unit is ``MB`` (an SI unit). As noted previously, :class:`BitmathFileTransferSpeed` allows for full control over the formatting of the calculated rate of transfer. For example, if we wished to see the rate printed using more verbose language and plauralized units, we could do exactly that by constructing our widget in the following way: .. code-block:: python BitmathFileTransferSpeed(format="{value:.2f} {unit_plural} per second") And if this were run from a script like the previous examples:: Something: 100% ||||||||||||||||||||||||||||||||||| Time: 0:00:01 9.41 MiBs per second