util: small clean-up re format_satoshis

related #4771

electrum/gui/qt/main_window.py

@@ -688,7 +688,7 @@ class ElectrumWindow(QMainWindow, MessageBoxMixin, PrintError):
         return text
 
     def format_fee_rate(self, fee_rate):
-        return format_fee_satoshis(fee_rate/1000, self.num_zeros) + ' sat/byte'
+        return format_fee_satoshis(fee_rate/1000, num_zeros=self.num_zeros) + ' sat/byte'
 
     def get_decimal_point(self):
         return self.decimal_point

electrum/tests/test_util.py

@@ -1,4 +1,6 @@
-from electrum.util import format_satoshis, parse_URI
+from decimal import Decimal
+
+from electrum.util import format_satoshis, format_fee_satoshis, parse_URI
 
 from . import SequentialTestCase
 
@@ -6,56 +8,38 @@ from . import SequentialTestCase
 class TestUtil(SequentialTestCase):
 
     def test_format_satoshis(self):
-        result = format_satoshis(1234)
+        self.assertEqual("0.00001234", format_satoshis(1234))
-        expected = "0.00001234"
-        self.assertEqual(expected, result)
 
     def test_format_satoshis_negative(self):
-        result = format_satoshis(-1234)
+        self.assertEqual("-0.00001234", format_satoshis(-1234))
-        expected = "-0.00001234"
-        self.assertEqual(expected, result)
 
     def test_format_fee(self):
-        result = format_satoshis(1700/1000, 0, 0)
+        self.assertEqual("1.7", format_fee_satoshis(1700/1000))
-        expected = "1.7"
-        self.assertEqual(expected, result)
 
     def test_format_fee_precision(self):
-        result = format_satoshis(1666/1000, 0, 0, precision=6)
+        self.assertEqual("1.666",
-        expected = "1.666"
+                         format_fee_satoshis(1666/1000, precision=6))
-        self.assertEqual(expected, result)
+        self.assertEqual("1.7",
-
+                         format_fee_satoshis(1666/1000, precision=1))
-        result = format_satoshis(1666/1000, 0, 0, precision=1)
-        expected = "1.7"
-        self.assertEqual(expected, result)
 
     def test_format_satoshis_whitespaces(self):
-        result = format_satoshis(12340, whitespaces=True)
+        self.assertEqual("     0.0001234 ",
-        expected = "     0.0001234 "
+                         format_satoshis(12340, whitespaces=True))
-        self.assertEqual(expected, result)
+        self.assertEqual("     0.00001234",
-
+                         format_satoshis(1234, whitespaces=True))
-        result = format_satoshis(1234, whitespaces=True)
-        expected = "     0.00001234"
-        self.assertEqual(expected, result)
 
     def test_format_satoshis_whitespaces_negative(self):
-        result = format_satoshis(-12340, whitespaces=True)
+        self.assertEqual("    -0.0001234 ",
-        expected = "    -0.0001234 "
+                         format_satoshis(-12340, whitespaces=True))
-        self.assertEqual(expected, result)
+        self.assertEqual("    -0.00001234",
-
+                         format_satoshis(-1234, whitespaces=True))
-        result = format_satoshis(-1234, whitespaces=True)
-        expected = "    -0.00001234"
-        self.assertEqual(expected, result)
 
     def test_format_satoshis_diff_positive(self):
-        result = format_satoshis(1234, is_diff=True)
+        self.assertEqual("+0.00001234",
-        expected = "+0.00001234"
+                         format_satoshis(1234, is_diff=True))
-        self.assertEqual(expected, result)
 
     def test_format_satoshis_diff_negative(self):
-        result = format_satoshis(-1234, is_diff=True)
+        self.assertEqual("-0.00001234", format_satoshis(-1234, is_diff=True))
-        expected = "-0.00001234"
-        self.assertEqual(expected, result)
 
     def _do_test_parse_URI(self, uri, expected):
         result = parse_URI(uri)

electrum/util.py

@@ -540,8 +540,11 @@ FEERATE_PRECISION = 1  # num fractional decimal places for sat/byte fee rates
 _feerate_quanta = Decimal(10) ** (-FEERATE_PRECISION)
 
 
-def format_fee_satoshis(fee, num_zeros=0):
+def format_fee_satoshis(fee, *, num_zeros=0, precision=None):
-    return format_satoshis(fee, num_zeros, 0, precision=FEERATE_PRECISION)
+    if precision is None:
+        precision = FEERATE_PRECISION
+    num_zeros = min(num_zeros, FEERATE_PRECISION)  # no more zeroes than available prec
+    return format_satoshis(fee, num_zeros=num_zeros, decimal_point=0, precision=precision)
 
 
 def quantize_feerate(fee):