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pylightning: adds msat.to_approx_str() method

Tries to return the approxmost posible string of a Millisatoshi amount using
various unit representations. The function will round to an effective
number of digits. Default: 3.

```
>>> Millisatoshi("100000sat").to_approx_str()
'0.001btc'
>>> Millisatoshi("100msat").to_approx_str()
'0.1sat'
>>> Millisatoshi("10000000sat").to_approx_str()
'0.1btc'
```
htlc_accepted_hook
Michael Schmoock 6 years ago
committed by Christian Decker
parent
commit
d8599e5f67
  1. 32
      contrib/pylightning/lightning/lightning.py

32
contrib/pylightning/lightning/lightning.py

@ -1,6 +1,7 @@
from decimal import Decimal from decimal import Decimal
import json import json
import logging import logging
from math import floor, log10
import socket import socket
__version__ = "0.0.7.1" __version__ = "0.0.7.1"
@ -85,6 +86,37 @@ class Millisatoshi:
else: else:
return '{:.8f}btc'.format(self.to_btc()) return '{:.8f}btc'.format(self.to_btc())
def to_approx_str(self, digits: int = 3):
"""Returns the shortmost string using common units representation.
Rounds to significant `digits`. Default: 3
"""
round_to_n = lambda x, n: round(x, -int(floor(log10(x))) + (n - 1))
result = None
# we try to increase digits to check if we did loose out on precision
# without gaining a shorter string, since this is a rarely used UI
# function, performance is not an issue. Adds at least one iteration.
while True:
# first round everything down to effective digits
amount_rounded = round_to_n(self.millisatoshis, digits)
# try different units and take shortest resulting normalized string
amounts_str = [
"%gbtc" % (amount_rounded / 1000 / 10**8),
"%gsat" % (amount_rounded / 1000),
"%gmsat" % (amount_rounded),
]
test_result = min(amounts_str, key=len)
# check result and do another run if necessary
if test_result == result:
return result
elif not result or len(test_result) <= len(result):
digits = digits + 1
result = test_result
else:
return result
def to_json(self): def to_json(self):
return self.__repr__() return self.__repr__()

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