eth-utils 1.0.3

Common utility functions for ethereum codebases.

Common utility functions for codebases which interact with ethereum.

This library and repository was previously located at https://github.com/pipermerriam/ethereum-utils. It was transferred to the Ethereum foundation github in November 2017 and renamed to eth-utils. The PyPi package was also renamed from ethereum-utils to `eth-utils.

Installation

pip install eth-utils

Development

Clone the repository and then run:

pip install -e .[dev] eth-hash[pycryptodome]

Running the tests

You can run the tests with:

py.test tests

Or you can install tox to run the full test suite.

Releasing

Pandoc is required for transforming the markdown README to the proper format to render correctly on pypi.

For Debian-like systems:

apt install pandoc

Or on OSX:

brew install pandoc

To release a new version:

make release bump=$$VERSION_PART_TO_BUMP$$

How to bumpversion

The version format for this repo is {major}.{minor}.{patch} for stable, and {major}.{minor}.{patch}-{stage}.{devnum} for unstable (stage can be alpha or beta).

To issue the next version in line, specify which part to bump, like make release bump=minor or make release bump=devnum.

If you are in a beta version, make release bump=stage will switch to a stable.

To issue an unstable version when the current version is stable, specify the new version explicitly, like make release bump="--new-version 4.0.0-alpha.1 devnum"

Documentation

All functions can be imported directly from the eth_utils module

Alternatively, you can get the curried version of the functions by importing them through the curried module like so:

from eth_utils.curried import hexstr_if_str

ABI Utils

event_abi_to_log_topic(event_abi) -> bytes

Returns the 32 byte log topic for the given event abi.

>>> event_abi_to_log_topic({'type': 'event', 'anonymous': False, 'name': 'MyEvent', 'inputs': []})
b'M\xbf\xb6\x8bC\xdd\xdf\xa1+Q\xeb\xe9\x9a\xb8\xfd\xedb\x0f\x9a\n\xc21B\x87\x9aO\x19*\x1byR\xd2'

event_signature_to_log_topic(event_signature) -> bytes

Returns the 32 byte log topic for the given event signature.

>>> event_signature_to_log_topic('MyEvent()')
b'M\xbf\xb6\x8bC\xdd\xdf\xa1+Q\xeb\xe9\x9a\xb8\xfd\xedb\x0f\x9a\n\xc21B\x87\x9aO\x19*\x1byR\xd2'

function_abi_to_4byte_selector(function_abi) -> bytes

Returns the 4 byte function selector for the given function abi.

>>> function_abi_to_4byte_selector({'type': 'function', 'name': 'myFunction', 'inputs': [], 'outputs': []})
b'\xc3x\n:'

function_signature_to_4byte_selector(function_signature) -> bytes

Returns the 4 byte function selector for the given function signature.

>>> function_signature_to_4byte_selector('myFunction()')
b'\xc3x\n:'

Applicators

Applicators help you apply “formatters” in various ways, most notably:

• apply formatters to values by key
• apply formatters to lists by index
• conditionally applying a formatter
• conditionally applying one of several formatters.

Here we define a “formatter” as any callable that may be called with a single positional argument. It returns the “formatted” result. For example int() could be used as a formatter.

Defining your own formatter is easy:

def i_put_my_thing_down_flip_it_and_reverse_it(lyric):
    return ''.join(reversed(lyric))

These tools often work nicely when curried. Import them from the curried module to get that capability built in, like from eth_utils.curried import apply_formatter_if.

apply_formatter_if(condition, formatter, value) -> new_value

This function will apply the formatter only if bool(condition()) is True.

>>> from eth_utils.curried import apply_formatter_if, is_string

>>> bool_if_string = apply_formatter_if(is_string, bool)

>>> bool_if_string(1)
1
>>> bool_if_string('1')
True
>>> bool_if_string('')
False

apply_one_of_formatters(condition_formatter_pairs, value) -> new_value

This function will iterate through condition_formatter_pairs, and apply the first formatter which has a truthy condition. One of the formatters must match, or this function will raise a ValueError.

>>> from eth_utils.curried import apply_one_of_formatters, is_string, is_list_like

>>> multi_formatter = apply_one_of_formatters((
    (is_list_like, tuple),
    (is_string, i_put_my_thing_down_flip_it_and_reverse_it),
)
>>> multi_formatter('my thing')
'gniht ym'
>>> multi_formatter([1, 2])
(1, 2)
>>> multi_formatter(54)
ValueError("The provided value did not satisfy any of the formatter conditions")

apply_formatter_at_index(formatter, at_index, <list_like>) ->

This function will apply the formatter to one element of list_like, at position at_index, and return a new iterable with that element replaced. The returned value will be the same type as the one passed into the third argument.

>>> from eth_utils.curried import apply_formatter_at_index

>>> targetted_formatter = apply_formatter_at_index(bool, 1)

>>> targetted_formatter((1, 2, 3))
(1, True, 3)

>>> targetted_formatter([1, 2, 3])
[1, True, 3]

apply_formatter_to_array(formatter, <list_like>) ->

This function will apply the formatter to each element of list_like. It returns the same type as the list_like argument

>>> from eth_utils.curried import apply_formatter_to_array

>>> map_int = apply_formatter_to_array(int)

>>> map_int((1.2, 3.4, 5.6))
(1, 3, 5)

>>> map_int([1.2, 3.4, 5.6])
[1, 3, 5]

apply_formatters_to_sequence(formatters, <list_like>) ->

This function will apply each formatter at to the list-like value, at the position it was supplied. It returns the same time as the list_like argument. For example:

>>> from eth_utils.curried import apply_formatters_to_sequence

>>> list_formatter = apply_formatters_to_sequence([bool, int, str])

>>> list_formatter([1.2, 3.4, 5.6])
[True, 3, '5.6']

>>> list_formatter((1.2, 3.4, 5.6))
(True, 3, '5.6')

# Formatters and list-like value must be the same length

>>> list_formatter((1.2, 3.4, 5.6, 7.8))
IndexError: Too few formatters for sequence: 3 formatters for (1.2, 3.4, 5.6, 7.8)

>>> list_formatter((1.2, 3.4))
IndexError: Too many formatters for sequence: 3 formatters for (1.2, 3.4)

combine_argument_formatters(*formatters) -> lambda :

DEPRECATED

You can replace all current versions of:

>>> from eth_utils import combine_argument_formatters

>>> list_formatter = combine_argument_formatters(bool, int, str)

With the newer, preferred:

>>> from eth_utils.curried import apply_formatters_to_sequence

>>> list_formatter = apply_formatters_to_sequence((bool, int, str))

The old usage works like:

Combine several formatters to be applied to a list-like value, each formatter at the position it was supplied. The new formatter will return the same type as it was supplied. For example:

>>> from eth_utils import combine_argument_formatters

>>> list_formatter = combine_argument_formatters(bool, int, str)

>>> list_formatter([1.2, 3.4, 5.6])
[True, 3, '5.6']

>>> list_formatter((1.2, 3.4, 5.6))
(True, 3, '5.6')

# it will pass through items longer than the number of formatters supplied
>>> list_formatter((1.2, 3.4, 5.6, 7.8))
[True, 3, '5.6', 7.8]

apply_formatters_to_dict(formatter_dict, <dict_like>) -> dict

This function will apply the formatter to the element with the matching key in dict_like, passing through values with keys that have no matching formatter.

>>> from eth_utils.curried import apply_formatters_to_dict

>>> dict_formatter = apply_formatters_to_dict({
    'should_be_int': int,
    'should_be_bool': bool,
})

>>> dict_formatter({
    'should_be_int': 1.2,
    'should_be_bool': 3.4,
    'pass_through': 5.6,
})
{
    'should_be_int': 1,
    'should_be_bool': True,
    'pass_through': 5.6,
}

apply_key_map(formatter_dict, <dict_like>) -> dict

This function will rename keys from using the lookups provided in formatter_dict. It will pass through any unspecified keys.

>>> from eth_utils.curried import apply_key_map

>>> dict_key_map = apply_key_map({
    'black': 'orange',
    'Internet': 'Ethereum',
})

>>> dict_key_map({
    'black': 1.2,
    'Internet': 3.4,
    'pass_through': 5.6,
})
{
    'orange': 1.2,
    'Ethereum': 3.4,
    'pass_through': 5.6,
}

Address Utils

is_address(value) -> bool

Returns True if the value is one of the following accepted address formats.

• 20 byte hexadecimal, upper/lower/mixed case, with or without 0x prefix:
  • 'd3cda913deb6f67967b99d67acdfa1712c293601'
  • '0xd3cda913deb6f67967b99d67acdfa1712c293601'
  • '0xD3CDA913DEB6F67967B99D67ACDFA1712C293601'
  • '0xd3CdA913deB6f67967B99D67aCDFa1712C293601'
• 20 byte hexadecimal padded to 32 bytes with null bytes, upper/lower/mixed case, with or without 0x prefix:
  • '000000000000000000000000d3cda913deb6f67967b99d67acdfa1712c293601'
  • '000000000000000000000000d3cda913deb6f67967b99d67acdfa1712c293601'
  • '0x000000000000000000000000d3cda913deb6f67967b99d67acdfa1712c293601'
  • '0x000000000000000000000000D3CDA913DEB6F67967B99D67ACDFA1712C293601'
  • '0x000000000000000000000000d3CdA913deB6f67967B99D67aCDFa1712C293601'
• 20 text or bytes string:
  • '\xd3\xcd\xa9\x13\xde\xb6\xf6yg\xb9\x9dg\xac\xdf\xa1q,)6\x01'
• 20 text or bytes string padded to 32 bytes with null bytes.
  • '\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\xd3\xcd\xa9\x13\xde\xb6\xf6yg\xb9\x9dg\xac\xdf\xa1q,)6\x01'

This function has two special cases when it will return False:

• a 20-byte hex string that has mixed case, with an invalid checksum
• a 32-byte value that is all null bytes

>>> is_address('d3cda913deb6f67967b99d67acdfa1712c293601')
True
>>> is_address('0xd3cda913deb6f67967b99d67acdfa1712c293601')
True
>>> is_address('0xD3CDA913DEB6F67967B99D67ACDFA1712C293601')
True
>>> is_address('0xd3CdA913deB6f67967B99D67aCDFa1712C293601')
True
>>> is_address('000000000000000000000000d3cda913deb6f67967b99d67acdfa1712c293601')
True
>>> is_address('000000000000000000000000d3cda913deb6f67967b99d67acdfa1712c293601')
True
>>> is_address('0x000000000000000000000000d3cda913deb6f67967b99d67acdfa1712c293601')
True
>>> is_address('0x000000000000000000000000D3CDA913DEB6F67967B99D67ACDFA1712C293601')
True
>>> is_address('0x000000000000000000000000d3CdA913deB6f67967B99D67aCDFa1712C293601')
True
>>> is_address('\xd3\xcd\xa9\x13\xde\xb6\xf6yg\xb9\x9dg\xac\xdf\xa1q,)6\x01')
True
>>> is_address('\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\xd3\xcd\xa9\x13\xde\xb6\xf6yg\xb9\x9dg\xac\xdf\xa1q,)6\x01')
True
>>> is_address('0x0000000000000000000000000000000000000000000000000000000000000000')
False
>>> is_address('\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00')
False

is_hex_address(value) => bool

Return True if the value is a 20 byte hexadecimal encoded string in any of upper/lower/mixed casing, with or without the 0x prefix. Otherwise return False

• 'd3cda913deb6f67967b99d67acdfa1712c293601'
• '0xd3cda913deb6f67967b99d67acdfa1712c293601'
• '0xD3CDA913DEB6F67967B99D67ACDFA1712C293601'
• '0xd3CdA913deB6f67967B99D67aCDFa1712C293601'

>>> is_hex_address('d3cda913deb6f67967b99d67acdfa1712c293601')
True
>>> is_hex_address('0xd3cda913deb6f67967b99d67acdfa1712c293601')
True
>>> is_hex_address('0xD3CDA913DEB6F67967B99D67ACDFA1712C293601')
True
>>> is_hex_address('0xd3CdA913deB6f67967B99D67aCDFa1712C293601')
True
>>> is_hex_address('000000000000000000000000d3cda913deb6f67967b99d67acdfa1712c293601')
False
>>> is_hex_address('000000000000000000000000d3cda913deb6f67967b99d67acdfa1712c293601')
False
>>> is_hex_address('0x000000000000000000000000d3cda913deb6f67967b99d67acdfa1712c293601')
False
>>> is_hex_address('0x000000000000000000000000D3CDA913DEB6F67967B99D67ACDFA1712C293601')
False
>>> is_hex_address('0x000000000000000000000000d3CdA913deB6f67967B99D67aCDFa1712C293601')
False
>>> is_hex_address('\xd3\xcd\xa9\x13\xde\xb6\xf6yg\xb9\x9dg\xac\xdf\xa1q,)6\x01')
False
>>> is_hex_address('\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\xd3\xcd\xa9\x13\xde\xb6\xf6yg\xb9\x9dg\xac\xdf\xa1q,)6\x01')
False
>>> is_hex_address('0x0000000000000000000000000000000000000000000000000000000000000000')
False
>>> is_hex_address('\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00')
False

is_binary_address(value) -> bool

Return True if the value is a 20 byte string.

>>> is_binary_address('d3cda913deb6f67967b99d67acdfa1712c293601')
False
>>> is_binary_address('0xd3cda913deb6f67967b99d67acdfa1712c293601')
False
>>> is_binary_address('0xD3CDA913DEB6F67967B99D67ACDFA1712C293601')
False
>>> is_binary_address('0xd3CdA913deB6f67967B99D67aCDFa1712C293601')
False
>>> is_binary_address('000000000000000000000000d3cda913deb6f67967b99d67acdfa1712c293601')
False
>>> is_binary_address('000000000000000000000000d3cda913deb6f67967b99d67acdfa1712c293601')
False
>>> is_binary_address('0x000000000000000000000000d3cda913deb6f67967b99d67acdfa1712c293601')
False
>>> is_binary_address('0x000000000000000000000000D3CDA913DEB6F67967B99D67ACDFA1712C293601')
False
>>> is_binary_address('0x000000000000000000000000d3CdA913deB6f67967B99D67aCDFa1712C293601')
False
>>> is_binary_address('\xd3\xcd\xa9\x13\xde\xb6\xf6yg\xb9\x9dg\xac\xdf\xa1q,)6\x01')
True
>>> is_binary_address('\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\xd3\xcd\xa9\x13\xde\xb6\xf6yg\xb9\x9dg\xac\xdf\xa1q,)6\x01')
False
>>> is_binary_address('0x0000000000000000000000000000000000000000000000000000000000000000')
False
>>> is_binary_address('\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00')
False

is_canonical_address(value) -> bool

Returns True if the value is an address in it’s canonical form.

The canonical representation of an address according to eth_utils is a 20 byte long string of bytes, eg: b'\xd3\xcd\xa9\x13\xde\xb6\xf6yg\xb9\x9dg\xac\xdf\xa1q,)6\x01'

>>> is_canonical_address('0xd3cda913deb6f67967b99d67acdfa1712c293601')
False
>>> is_canonical_address(b'\xd3\xcd\xa9\x13\xde\xb6\xf6yg\xb9\x9dg\xac\xdf\xa1q,)6\x01xd')
True
>>> is_canonical_address('\xd3\xcd\xa9\x13\xde\xb6\xf6yg\xb9\x9dg\xac\xdf\xa1q,)6\x01xd')
False

is_checksum_address(value) -> bool

Returns True if the value is a checksummed address as specified by ERC55

>>> is_checksum_address('0xd3CdA913deB6f67967B99D67aCDFa1712C293601')
True
>>> is_checksum_address('0xd3cda913deb6f67967b99d67acdfa1712c293601')
False
>>> is_checksum_address('0xD3CDA913DEB6F67967B99D67ACDFA1712C293601')
False
>>> is_checksum_address('0x52908400098527886E0F7030069857D2E4169EE7')
True
>>> is_checksum_address('0xde709f2102306220921060314715629080e2fb77')
True

is_checksum_formatted_address(value) -> bool

Returns True if the value is formatted as an ERC55 checksum address.

>>> is_checksum_formatted_address('0xd3CdA913deB6f67967B99D67aCDFa1712C293601')
True
>>> is_checksum_formatted_address('0xd3cda913deb6f67967b99d67acdfa1712c293601')
False
>>> is_checksum_formatted_address('0xD3CDA913DEB6F67967B99D67ACDFA1712C293601')
False
>>> is_checksum_formatted_address('0x52908400098527886E0F7030069857D2E4169EE7')
False
>>> is_checksum_formatted_address('0xde709f2102306220921060314715629080e2fb77')
False

is_normalized_address(value) -> bool

Returns True if the value is an address in its normalized form.

The normalized representation of an address is the lowercased 20 byte hexadecimal format.

>>> is_normalized_address('0xd3CdA913deB6f67967B99D67aCDFa1712C293601')
False
>>> is_normalized_address('0xd3cda913deb6f67967b99d67acdfa1712c293601')
True
>>> is_normalized_address('0xD3CDA913DEB6F67967B99D67ACDFA1712C293601')
False
>>> is_normalized_address('0x52908400098527886E0F7030069857D2E4169EE7')
False
>>> is_normalized_address('0xde709f2102306220921060314715629080e2fb77')
True

is_same_address(a, b) -> bool

Returns True if both a and b are valid addresses according to the is_address function and that they are both representations of the same address.

>>> is_same_address('0xd3cda913deb6f67967b99d67acdfa1712c293601', '0xD3CDA913DEB6F67967B99D67ACDFA1712C293601')
True
>>> is_same_address('0xd3cda913deb6f67967b99d67acdfa1712c293601', '0xd3CdA913deB6f67967B99D67aCDFa1712C293601')
True
>>> is_same_address('0xd3cda913deb6f67967b99d67acdfa1712c293601', '\xd3\xcd\xa9\x13\xde\xb6\xf6yg\xb9\x9dg\xac\xdf\xa1q,)6\x01xd')
True

to_canonical_address(value) -> bytes

Given any valid representation of an address return it’s canonical form.

>>> to_canonical_address('0xd3cda913deb6f67967b99d67acdfa1712c293601')
b'\xd3\xcd\xa9\x13\xde\xb6\xf6yg\xb9\x9dg\xac\xdf\xa1q,)6\x01xd'
>>> to_canonical_address('0xD3CDA913DEB6F67967B99D67ACDFA1712C293601')
b'\xd3\xcd\xa9\x13\xde\xb6\xf6yg\xb9\x9dg\xac\xdf\xa1q,)6\x01xd'
>>> to_canonical_address('0xd3CdA913deB6f67967B99D67aCDFa1712C293601')
b'\xd3\xcd\xa9\x13\xde\xb6\xf6yg\xb9\x9dg\xac\xdf\xa1q,)6\x01xd'
>>> to_canonical_address('\xd3\xcd\xa9\x13\xde\xb6\xf6yg\xb9\x9dg\xac\xdf\xa1q,)6\x01xd')
b'\xd3\xcd\xa9\x13\xde\xb6\xf6yg\xb9\x9dg\xac\xdf\xa1q,)6\x01xd'

to_checksum_address(value) -> text

Given any valid representation of an address return the checksummed representation.

>>> to_checksum_address('0xd3cda913deb6f67967b99d67acdfa1712c293601')
'0xd3CdA913deB6f67967B99D67aCDFa1712C293601'
>>> to_checksum_address('0xD3CDA913DEB6F67967B99D67ACDFA1712C293601')
'0xd3CdA913deB6f67967B99D67aCDFa1712C293601'
>>> to_checksum_address('0xd3CdA913deB6f67967B99D67aCDFa1712C293601')
'0xd3CdA913deB6f67967B99D67aCDFa1712C293601'
>>> to_checksum_address('\xd3\xcd\xa9\x13\xde\xb6\xf6yg\xb9\x9dg\xac\xdf\xa1q,)6\x01xd')
'0xd3CdA913deB6f67967B99D67aCDFa1712C293601'

to_normalized_address(value) -> text

Given any valid representation of an address return the normalized representation.

>>> to_normalized_address('\xd3\xcd\xa9\x13\xde\xb6\xf6yg\xb9\x9dg\xac\xdf\xa1q,)6\x01')  # raw bytes
'0xd3cda913deb6f67967b99d67acdfa1712c293601'
>>> to_normalized_address(b'0xc6d9d2cd449a754c494264e1809c50e34d64562b')  # hex encoded (as byte string)
'0xc6d9d2cd449a754c494264e1809c50e34d64562b'
>>> to_normalized_address('0xc6d9d2cd449a754c494264e1809c50e34d64562b')  # hex encoded
'0xc6d9d2cd449a754c494264e1809c50e34d64562b'
>>> to_normalized_address('0XC6D9D2CD449A754C494264E1809C50E34D64562B')  # cap-cased
'0xc6d9d2cd449a754c494264e1809c50e34d64562b'
>>> to_normalized_address('0x000000000000000000000000c305c901078781c232a2a521c2af7980f8385ee9')  # padded to 32 bytes
'0xc305c901078781c232a2a521c2af7980f8385ee9',

Conversion Utils

These methods convert values using standard practices in the Ethereum ecosystem. For example, strings are encoded to binary using UTF-8.

Because there is no reliable way to distinguish between text and a hex-encoded bytestring, you must explicitly specify which of the two is being supplied when passing in a str.

Only supply one of the arguments:

to_bytes(<bytes/int/bool>, text=<str>, hexstr=<str>) -> bytes

Takes a variety of inputs and returns its bytes equivalent. Text gets encoded as UTF-8.

>>> to_bytes(0)
b'\x00'
>>> to_bytes(0x000F)
b'\x0f'
>>> to_bytes(b'')
b''
>>> to_bytes(b'\x00\x0F')
b'\x00\x0f'
>>> to_bytes(False)
b'\x00'
>>> to_bytes(True)
b'\x01'
>>> to_bytes(hexstr='0x000F')
b'\x00\x0f'
>>> to_bytes(hexstr='000F')
b'\x00\x0f'
>>> to_bytes(text='')
b''
>>> to_bytes(text='cowmö')
b'cowm\xc3\xb6'

to_hex(<bytes/int/bool>, text=<str>, hexstr=<str>) -> str

Takes a variety of inputs and returns it in its hexadecimal representation. It follows the rules for converting to hex in the JSON-RPC spec. Roughly, it leaves leading 0s on bytes input, and trims leading zeros on int input.

>>> to_hex(0)
'0x0'
>>> to_hex(1)
'0x1'
>>> to_hex(0x0)
'0x0'
>>> to_hex(0x000F)
'0xf'
>>> to_hex(b'')
'0x'
>>> to_hex(b'\x00\x0F')
'0x000f'
>>> to_hex(False)
'0x0'
>>> to_hex(True)
'0x1'
>>> to_hex(hexstr='0x000F')
'0x000f'
>>> to_hex(hexstr='000F')
'0x000f'
>>> to_hex(text='')
'0x'
>>> to_hex(text='cowmö')
'0x636f776dc3b6'

to_int(<bytes/int/bool>, text=<str>, hexstr=<str>) -> int

Takes a variety of inputs and returns its integer equivalent.

>>> to_int(0)
0
>>> to_int(0x000F)
15
>>> to_int(b'\x00\x0F')
15
>>> to_int(False)
0
>>> to_int(True)
1
>>> to_int(hexstr='0x000F')
15
>>> to_int(hexstr='000F')
15

to_text(<bytes/int/bool>, text=<str>, hexstr=<str>) -> str

Takes a variety of inputs and returns its string equivalent. Text gets decoded as UTF-8.

>>> Web3.toText(0x636f776dc3b6)
'cowmö'
>>> Web3.toText(b'cowm\xc3\xb6')
'cowmö'
>>> Web3.toText(hexstr='0x636f776dc3b6')
'cowmö'
>>> Web3.toText(hexstr='636f776dc3b6')
'cowmö'
>>> Web3.toText(text='cowmö')
'cowmö'

Crypto Utils

Because there is no reliable way to distinguish between text and a hex-encoded bytestring, you must explicitly specify which of the two is being supplied when passing in a str.

Only supply one of the arguments:

keccak(<bytes/int/bool>, text=<str>, hexstr=<str>) -> bytes

>>> keccak(text='')
b"\xc5\xd2F\x01\x86\xf7#<\x92~}\xb2\xdc\xc7\x03\xc0\xe5\x00\xb6S\xca\x82';{\xfa\xd8\x04]\x85\xa4p"

# A series of equivalent hash inputs:

>>> keccak(text='☢')
b'\x85\xe8\x07"\xeb\x93\r\xe9;\xcc\xa8{\xa5\xdf\xda\x89\n\xa12\x95\xae\xad.\xec\xc9\x0b\xb2\xd9z\x14\x93\x16'

>>> keccak(0xe298a2)
b'\x85\xe8\x07"\xeb\x93\r\xe9;\xcc\xa8{\xa5\xdf\xda\x89\n\xa12\x95\xae\xad.\xec\xc9\x0b\xb2\xd9z\x14\x93\x16'

>>> keccak(b'\xe2\x98\xa2')
b'\x85\xe8\x07"\xeb\x93\r\xe9;\xcc\xa8{\xa5\xdf\xda\x89\n\xa12\x95\xae\xad.\xec\xc9\x0b\xb2\xd9z\x14\x93\x16'

>>> keccak(hexstr='0xe298a2')
b'\x85\xe8\x07"\xeb\x93\r\xe9;\xcc\xa8{\xa5\xdf\xda\x89\n\xa12\x95\xae\xad.\xec\xc9\x0b\xb2\xd9z\x14\x93\x16'

Please Note - When using Python’s native hex literals, python converts the hex to an int, so leading 0 bytes are truncated. But all other formats maintain zeros on the left. Hex literals are only padded until a whole number of bytes are provided to keccak. For example:

>>> keccak(0xe298a2)
b'\x85\xe8\x07"\xeb\x93\r\xe9;\xcc\xa8{\xa5\xdf\xda\x89\n\xa12\x95\xae\xad.\xec\xc9\x0b\xb2\xd9z\x14\x93\x16'

>>> keccak(0x0e298a2)
b'\x85\xe8\x07"\xeb\x93\r\xe9;\xcc\xa8{\xa5\xdf\xda\x89\n\xa12\x95\xae\xad.\xec\xc9\x0b\xb2\xd9z\x14\x93\x16'

>>> keccak(0x00e298a2)
b'\x85\xe8\x07"\xeb\x93\r\xe9;\xcc\xa8{\xa5\xdf\xda\x89\n\xa12\x95\xae\xad.\xec\xc9\x0b\xb2\xd9z\x14\x93\x16'

>>> keccak(0x000e298a2)
b'\x85\xe8\x07"\xeb\x93\r\xe9;\xcc\xa8{\xa5\xdf\xda\x89\n\xa12\x95\xae\xad.\xec\xc9\x0b\xb2\xd9z\x14\x93\x16'

>>> keccak(hexstr='0x0e298a2')
b'i\x0f$\xbd\xbe\xf7c\xbb\xb9M\xd9\x12H"\x9f\x1f\x87\\E\xa36\xc2\xea,\x8f.\r\xf5\x95\xdc\x19\x9b'

>>> keccak(hexstr='0x00e298a2')
b'i\x0f$\xbd\xbe\xf7c\xbb\xb9M\xd9\x12H"\x9f\x1f\x87\\E\xa36\xc2\xea,\x8f.\r\xf5\x95\xdc\x19\x9b'

>>> keccak(hexstr='0x000e298a2')
b'!$Ezy\xdeU<\xec\x1f\xd1\x10\x05\xff\x11\xfc=J\xcf\xd5H\x0f\xb3c\xcc\xb5\xae\xb1\x1eA\x8b\xd3'

Currency Utils

denoms

Object with property access to all of the various denominations for ether. Available denominations are:

denomination	amount in wei
wei kwei babbage femtoether mwei lovelace picoether gwei shannon nanoether nano szabo microether micro finney milliether milli ether kether grand mether gether tether	1 1000 1000 1000 1000000 1000000 1000000 1000000000 1000000000 1000000000 1000000000 1000000000000 1000000000000 1000000000000 1000000000000000 1000000000000000 1000000000000000 1000000000000000000 1000000000000000000000 1000000000000000000000 1000000000000000000000000 1000000000000000000000000000 1000000000000000000000000000000

>>> denoms.wei
1
>>> denoms.finney
1000000000000000
>>> denoms.ether
1000000000000000000

to_wei(value, denomination) -> integer

Converts value in the given denomination to its equivalent in the wei denomination.

>>> to_wei(1, 'ether')
1000000000000000000

from_wei(value, denomination) -> decimal.Decimal

Converts the value in the wei denomination to its equivalent in the given denomination. Return value is a decimal.Decimal with the appropriate precision to be a lossless conversion.

>>> from_wei(1000000000000000000, 'ether')
Decimal('1')
>>> from_wei(123456789, 'ether')
Decimal('1.23456789E-10')

Debug Utils

Generate environment info

At the shell:

$ python -m eth_utils

Python version:
3.5.3 (default, Nov 23 2017, 11:34:05)
[GCC 6.3.0 20170406]

Operating System: Linux-4.10.0-42-generic-x86_64-with-Ubuntu-17.04-zesty

pip freeze result:
bumpversion==0.5.3
cytoolz==0.9.0
flake8==3.4.1
ipython==6.2.1
pytest==3.3.2
virtualenv==15.1.0
... etc

Decorators

@combomethod

Decorates methods in a class that can be called as both an instance method or a @classmethod.

Use the decorator like so:

from eth_utils import combomethod

class Storage:
    val = 1

    @combomethod
    def get(combo):
        if isinstance(combo, type):
            print("classmethod call")
        elif isinstance(combo, Storage):
            print("instance method call")
        else:
            raise TypeError("Unreachable, unless you really monkey around")
        return combo.val

As usual, instances create their own copy on assignment.

>>> store = Storage()
>>> store.val = 2
>>> store.get()
instance method call
2
>>> Storage.get()
classmethod call
1

Encoding Utils

big_endian_to_int(value) -> integer

Returns value converted to an integer (from a big endian representation).

>>> big_endian_to_int(b'\x00')
0
>>> big_endian_to_int(b'\x01')
1
>>> big_endian_to_int(b'\x01\x00')
256

int_to_big_endian(value) -> bytes

Returns value converted to the big endian representation.

>>> int_to_big_endian(0)
b'\x00'
>>> int_to_big_endian(1)
b'\x01'
>>> int_to_big_endian(256)
b'\x01\x00'

Functional Utils

compose(*callables) -> callable

DEPRECATED in 0.3.0.

Returns a single function which is the composition of the given callables.

>>> def f(v):
...     return v * 3
...
>>> def g(v):
...     return v + 2
...
>>> def h(v):
...     return v % 5
...
>>> compose(f, g, h)(1)
0
>>> h(g(f(1)))
0
>>> compose(f, g, h)(2)
3
>>> h(g(f(1)))
3
>>> compose(f, g, h)(3)
1
>>> h(g(f(1)))
1
>>> compose(f, g, h)(4)
4
>>> h(g(f(1)))
4

flatten_return(callable) -> callable() -> tuple

Decorator which performs a non-recursive flattening of the return value from the given callable.

>>> flatten_return(lambda: [[1, 2, 3], [4, 5], [6]])
(1, 2, 3, 4, 5, 6)

sort_return(callable) => callable() -> tuple

Decorator which sorts the return value from the given callable.

>>> flatten_return(lambda: [[1, 2, 3], [4, 5], [6]])
(1, 2, 3, 4, 5, 6)

reversed_return(callable) => callable() -> tuple

Decorator which reverses the return value from the given callable.

>>> reversed_return(lambda: [1, 5, 2, 4, 3])
(3, 4, 2, 5, 1)

to_dict(callable) => callable() -> dict

Decorator which casts the return value from the given callable to a dictionary.

>>> @to_dict
... def build_thing():
...     yield 'a', 1
...     yield 'b', 2
...     yield 'c', 3
...
>>> build_thing()
{'a': 1, 'b': 2, 'c': 3}

to_list(callable) => callable() -> list

Decorator which casts the return value from the given callable to a list.

>>> @to_list
... def build_thing():
...     yield 'a'
...     yield 'b'
...     yield 'c'
...
>>> build_thing()
['a', 'b', 'c']

to_ordered_dict(callable) => callable() -> collections.OrderedDict

Decorator which casts the return value from the given callable to an ordered dictionary of type collections.OrderedDict.

>>> @to_ordered_dict
... def build_thing():
...     yield 'd', 4
...     yield 'a', 1
...     yield 'b', 2
...     yield 'c', 3
...
>>> build_thing()
OrderedDict([('d', 4), ('a', 1), ('b', 2), ('c', 3)])

to_tuple(callable) => callable() -> tuple

Decorator which casts the return value from the given callable to a tuple.

>>> @to_tuple
... def build_thing():
...     yield 'a'
...     yield 'b'
...     yield 'c'
...
>>> build_thing()
('a', 'b', 'c')

to_set(callable) => callable() -> set

Decorator which casts the return value from the given callable to a set.

>>> @to_set
... def build_thing():
...     yield 'a'
...     yield 'b'
...     yield 'a'  # duplicate
...     yield 'c'
...
>>> build_thing()
{'a', 'b', 'c'}

apply_to_return_value(callable) => decorator_fn

This function takes a single callable and returns a decorator. The returned decorator, when applied to a function, will incercept the function’s return value, pass it to the callable, and return the value returned by the callable.

>>> double = apply_to_return_value(lambda v: v * 2)
>>> @double
... def f(v):
...     return v
...
>>> f(2)
4
>>> f(3)
6

Hexidecimal Utils

add_0x_prefix(value) -> string

Returns value with a 0x prefix. If the value is already prefixed it is returned as-is.

>>> add_0x_prefix('12345')
'0x12345'
>>> add_0x_prefix('0x12345')
'0x12345'

decode_hex(value) -> bytes

Returns value decoded into a byte string. Accepts any string with or without the 0x prefix.

>>> decode_hex('0x123456')
b'\x124V'
>>> decode_hex('123456')
b'\x124V'

encode_hex(value) -> string

Returns value encoded into a hexadecimal representation with a 0x prefix

>>> encode_hex('\x01\x02\x03')
'0x010203'

is_0x_prefixed(value) -> bool

Returns True if value has a 0x prefix.

>>> is_0x_prefixed('12345')
False
>>> is_0x_prefixed('0x12345')
True
>>> is_0x_prefixed(b'0x12345')
True

is_hex(value) -> bool

Returns True if value is a hexadecimal encoded string of text type.

>>> is_hex('')
False
>>> is_hex(b'')
False
>>> is_hex('0x')
True
>>> is_hex(b'0x')
False
>>> is_hex('0X')
True
>>> is_hex(b'0X')
False
>>> is_hex('1234567890abcdef')
True
>>> is_hex('0x1234567890abcdef')
True
>>> is_hex('0x1234567890ABCDEF')
True
>>> is_hex('0x1234567890AbCdEf')
True
>>> is_hex('12345')  # odd length is ok
True
>>> is_hex('0x12345')  # odd length is ok
True
>>> is_hex('123456__abcdef')  # non hex characters
False

remove_0x_prefix(value) -> string

Returns value with the 0x prefix stripped. If the value does not have a 0x prefix it is returned as-is.

>>> remove_0x_prefix('12345')
'12345'
>>> remove_0x_prefix('0x12345')
'12345'
>>> remove_0x_prefix(b'0x12345')
b'12345'

Type Utils

is_boolean(value) -> bool

Returns True if value is of type bool

>>> is_boolean(True)
True
>>> is_boolean(False)
False
>>> is_boolean(1)
False

is_bytes(value) -> bool

Returns True if value is a byte string or a byte array.

>>> is_bytes('abcd')
False
>>> is_bytes(b'abcd')
True
>>> is_bytes(bytearray((1, 2, 3)))
True

is_dict(value) -> bool

Returns True if value is a mapping type.

>>> is_dict({'a': 1})
True
>>> is_dict([1, 2, 3])
False

is_integer(value) -> bool

Returns True if value is an integer

>>> is_integer(0)
True
>>> is_integer(1)
True
>>> is_integer('1')
False
>>> is_integer(1.1)
False

is_list_like(value) -> bool

Returns True if value is a non-string sequence such as a sequence (such as a list or tuple).

>>> is_list_like('abcd')
False
>>> is_list_like([])
True
>>> is_list_like(tuple())
True

is_list(value) -> bool

Returns True if value is a non-string sequence such as a list.

>>> is_list('abcd')
False
>>> is_list([])
True
>>> is_list(tuple())
False

is_tuple(value) -> bool

Returns True if value is a non-string sequence such as a tuple.

>>> is_tuple('abcd')
False
>>> is_tuple([])
False
>>> is_tuple(tuple())
True

is_null(value) -> bool

Returns True if value is None

>>> is_null(None)
True
>>> is_null(False)
False

is_number(value) -> bool

Returns True if value is numeric

>>> is_number(1)
True
>>> is_number(1.1)
True
>>> is_number('1')
False
>>> is_number(decimal.Decimal('1'))
True

is_string(value) -> bool

Returns True if value is of any string type.

>>> is_string('abcd')
True
>>> is_string(b'abcd')
True
>>> is_string(bytearray((1, 2, 3)))
True

is_text(value) -> bool

Returns True if value is a text string.

>>> is_text(u'abcd')
True
>>> is_text(b'abcd')
False
>>> is_text(bytearray((1, 2, 3)))
False

How to bumpversion

The version format for this repo is {major}.{minor}.{patch} for stable, and {major}.{minor}.{patch}-{stage}.{devnum} for unstable (stage can be alpha or beta).

To issue the next version in line, use bumpversion and specify which part to bump, like bumpversion minor or bumpversion devnum.

If you are in a beta version, bumpversion stage will switch to a stable.

To issue an unstable version when the current version is stable, specify the new version explicitly, like bumpversion --new-version 4.0.0-alpha.1 devnum