Using uevent instead of the separate files reduces I/O...

...and makes the code a bit cleaner.

Didn't touch much of the class logic, except that it just
displays the charge if the state is "Unknown".

i3pystatus/batterychecker.py

@@ -3,6 +3,47 @@
 
 from i3pystatus import IntervalModule
 
+class Battery:
+    """
+    Simple interface to /sys/class/power_supply/BATx/uevent
+
+    The data from uevent is transformed into attributes of this class, stripping
+    their prefix. (i.e. POWER_SUPPLY_NAME becomes the NAME attribute).
+
+    Numbers are automatically converted to floats.
+
+    Strings are stripped.
+
+    (configparser would be a bit overkill for this)
+    """
+
+    prefix = "POWER_SUPPLY_"
+
+    @staticmethod
+    def lchop(string, substring):
+        if string.startswith(substring):
+            return string[len(substring):]
+
+        return string
+
+    def __init__(self, file):
+        self.parse(file)
+
+    def parse(self, file):
+        with open(file, "r") as file:
+            for line in file:
+                self.parse_line(line.strip())
+
+    def parse_line(self, line):
+        key, value = line.split("=", 2)
+        key = self.lchop(key, self.prefix)
+        value = value.strip()
+
+        if value.isdecimal():
+            value = float(value)
+
+        setattr(self, key, value)
+
 class BatteryChecker(IntervalModule):
     """ 
     This class uses the /proc/acpi/battery interface to check for the
@@ -11,22 +52,21 @@ class BatteryChecker(IntervalModule):
     
     def __init__(self, battery_ident="BAT0"):
         self.battery_ident = battery_ident
-        self.base_path = "/sys/class/power_supply/%s" % self.battery_ident
+        self.base_path = "/sys/class/power_supply/{0}/uevent".format(self.battery_ident)
 
     def run(self):
         urgent = False
         color = "#ffffff"
-        status = open('%s/status' % self.base_path, 'r').readline().strip()
-        energy_now = float(open('%s/energy_now' % self.base_path, 'r').readline())
 
-        if status == 'Full':
-            full_text = 'fully charged'
-        elif status == 'Charging':
-            energy_full = float(open('%s/energy_full' % self.base_path, 'r').readline())
-            energy_percentage = (energy_now / energy_full) * 100
-            full_text = '%.2f%% charged'
-        elif status == 'Discharging':
-            power_now = float(open('%s/power_now' % self.base_path, 'r').readline())
+        battery = Battery(self.base_path)
+
+        status = battery.STATUS
+        energy_now = battery.ENERGY_NOW
+
+        if status == "Full":
+            full_text = "fully charged"
+        elif status == "Discharging":
+            power_now = battery.POWER_NOW
             remaining_time_secs = (energy_now / power_now) * 3600
             hours, remainder = divmod(remaining_time_secs, 3600)
             minutes, seconds = divmod(remainder, 60)
@@ -34,8 +74,10 @@ class BatteryChecker(IntervalModule):
             if remaining_time_secs < (15*60):
                 urgent = True
                 color = "#ff0000"
-        else:
-            full_text = 'n/a'
+        else: # Charging, Unknown etc. (My thinkpad says Unknown if close to fully charged)
+            energy_full = battery.ENERGY_FULL
+            percentage = (energy_now / energy_full) * 100
+            full_text = "%.2f%% charged" % percentage
 
         self.output = {
             "full_text": full_text,