python-escpos · patkan · Jul 27, 2026 · Sep 11, 2025 · Sep 11, 2025 · Sep 14, 2025
diff --git a/src/escpos/config.py b/src/escpos/config.py
@@ -2,6 +2,7 @@
 
 This module contains the implementations of abstract base class :py:class:`Config`.
 """
+
 import os
 import pathlib
 
@@ -30,7 +31,7 @@ def __init__(self) -> None:
         self._has_loaded = False
         self._printer = None
 
-        self._printer_name = None
+        self._printer_name = ""
         self._printer_config = None
 
     def _reset_config(self) -> None:
@@ -41,17 +42,43 @@ def _reset_config(self) -> None:
         """
         self._has_loaded = False
         self._printer = None
-
-        self._printer_name = None
+        self._printer_name = ""
         self._printer_config = None
 
-    def load(self, config_path=None):
+    def _set_config(self, config) -> None:
+        """Set configuration variables.
+
+        :param config: config object loaded from file or string.
+        """
+        self._printer_config = config.get("printer", None)
+        if self._printer_config is None:
+            self._has_loaded = True
+            return
+        printer_name = self._printer_config.get("type", "")
+        class_names = {
+            "usb": "Usb",
+            "serial": "Serial",
+            "network": "Network",
+            "file": "File",
+            "dummy": "Dummy",
+            "cupsprinter": "CupsPrinter",
+            "lp": "LP",
+            "win32raw": "Win32Raw",
+        }
+        self._printer_name = class_names.get(printer_name.lower(), printer_name)
+        if not self._printer_name or not hasattr(printer, self._printer_name):
+            raise exceptions.ConfigSyntaxError(
+                f'Printer type "{self._printer_name}" is invalid'
+            )
+
+        self._has_loaded = True
+
+    def load(self, config_path=None) -> None:
         """Load and parse the configuration file using pyyaml.
 
         :param config_path: An optional file path, file handle, or byte string
             for the configuration file.
         """
-        self._reset_config()
 
         if not config_path:
             config_path = os.path.join(
@@ -66,35 +93,25 @@ def load(self, config_path=None):
 
         try:
             with open(config_path, "rb") as config_file:
-                config = yaml.safe_load(config_file)
+                self.load_yaml_string(config_file)
         except EnvironmentError:
             raise exceptions.ConfigNotFoundError(
                 f"Couldn't read config at {config_path}"
             )
+
+    def load_yaml_string(self, yaml_string) -> None:
+        """Load and parse a yaml configuration string or file-like object.
+
+        :param yaml_string: A string or file-like object containing yaml formatted configuration.
+        """
+        self._reset_config()
+
+        try:
+            config = yaml.safe_load(yaml_string)
         except yaml.YAMLError:
             raise exceptions.ConfigSyntaxError("Error parsing YAML")
 
-        if "printer" in config:
-            self._printer_config = config["printer"]
-            printer_name = self._printer_config.pop("type")
-            class_names = {
-                "usb": "Usb",
-                "serial": "Serial",
-                "network": "Network",
-                "file": "File",
-                "dummy": "Dummy",
-                "cupsprinter": "CupsPrinter",
-                "lp": "LP",
-                "win32raw": "Win32Raw",
-            }
-            self._printer_name = class_names.get(printer_name.lower(), printer_name)
-
-            if not self._printer_name or not hasattr(printer, self._printer_name):
-                raise exceptions.ConfigSyntaxError(
-                    f'Printer type "{self._printer_name}" is invalid'
-                )
-
-        self._has_loaded = True
+        self._set_config(config)
 
     def printer(self):
         """Return a printer that was defined in the config.

diff --git a/test/test_config.py b/test/test_config.py
@@ -14,7 +14,7 @@
 import escpos.exceptions
 
 
-def generate_dummy_config(path, content=None):
+def generate_dummy_config(path, content=None) -> None:
     """Generate a dummy config in path"""
     dummy_config_content = content
     if not content:
@@ -23,15 +23,15 @@ def generate_dummy_config(path, content=None):
     assert path.read_text() == dummy_config_content
 
 
-def simple_printer_test(config):
+def simple_printer_test(config) -> None:
     """Simple test for the dummy printer."""
     p = config.printer()
     p._raw(b"1234")
 
     assert p.output == b"1234"
 
 
-def test_config_load_with_invalid_config_yaml(tmp_path):
+def test_config_load_with_invalid_config_yaml(tmp_path) -> None:
     """Test the loading of a config with a invalid config file (yaml issue)."""
     # generate a dummy config
     config_file = tmp_path / "config.yaml"
@@ -45,7 +45,7 @@ def test_config_load_with_invalid_config_yaml(tmp_path):
         c.load(config_path=config_file)
 
 
-def test_config_load_with_invalid_config_content(tmp_path):
+def test_config_load_with_invalid_config_content(tmp_path) -> None:
     """Test the loading of a config with a invalid config file (content issue)."""
     # generate a dummy config
     config_file = tmp_path / "config.yaml"
@@ -61,7 +61,7 @@ def test_config_load_with_invalid_config_content(tmp_path):
         c.load(config_path=config_file)
 
 
-def test_config_load_with_missing_config(tmp_path):
+def test_config_load_with_missing_config(tmp_path) -> None:
     """Test the loading of a config that does not exist."""
     # test the config loading
     from escpos import config
@@ -94,7 +94,7 @@ def test_config_load_from_appdir() -> None:
     simple_printer_test(c)
 
 
-def test_config_load_with_file(tmp_path):
+def test_config_load_with_file(tmp_path) -> None:
     """Test the loading of a config with a config file."""
     # generate a dummy config
     config_file = tmp_path / "config.yaml"
@@ -110,7 +110,7 @@ def test_config_load_with_file(tmp_path):
     simple_printer_test(c)
 
 
-def test_config_load_with_path(tmp_path):
+def test_config_load_with_path(tmp_path) -> None:
     """Test the loading of a config with a config path."""
     # generate a dummy config
     config_file = tmp_path / "config.yaml"
@@ -124,3 +124,49 @@ def test_config_load_with_path(tmp_path):
 
     # test the resulting printer object
     simple_printer_test(c)
+
+
+def test_config_load_yaml_string_with_invalid_config_yaml() -> None:
+    """Invalid YAML string should raise ConfigSyntaxError."""
+    from escpos import config
+
+    c = config.Config()
+    with pytest.raises(escpos.exceptions.ConfigSyntaxError):
+        c.load_yaml_string("}invalid}yaml}")
+
+
+def test_config_load_yaml_string_with_invalid_config_content() -> None:
+    """Invalid content should raise ConfigSyntaxError."""
+    from escpos import config
+
+    c = config.Config()
+    with pytest.raises(escpos.exceptions.ConfigSyntaxError):
+        c.load_yaml_string("printer:\n   type: NoPrinterWithThatName\n")
+
+
+def test_config_load_yaml_string_with_valid_config() -> None:
+    """Valid YAML string should produce a Dummy printer."""
+    from escpos import config
+
+    c = config.Config()
+    c.load_yaml_string("printer:\n   type: Dummy\n")
+    simple_printer_test(c)
+
+
+def test_config_load_with_empty_printer_section() -> None:
+    """Config with an empty printer section should raise ConfigSyntaxError."""
+    from escpos import config
+
+    c = config.Config()
+    with pytest.raises(escpos.exceptions.ConfigSyntaxError):
+        c.load_yaml_string("printer: {}")
+
+
+def test_config_load_yaml_string_without_printer_section() -> None:
+    """Config without a printer section should raise ConfigSectionMissingError."""
+    from escpos import config
+
+    c = config.Config()
+    c.load_yaml_string("{}")
+    with pytest.raises(escpos.exceptions.ConfigSectionMissingError):
+        c.printer()