sqlite-utils convert db table column -, refs #353

docs/cli.rst

@@ -1023,6 +1023,16 @@ You can specify Python modules that should be imported and made available to you
         '"\n".join(textwrap.wrap(value, 100))' \
         --import=textwrap
 
+Use a CODE value of `-` to read from standard input:
+
+    $ cat mycode.py | sqlite-utils convert content.db articles headline -
+
+Where `mycode.py` contains a fragment of Python code that looks like this:
+
+```python
+return value.upper()
+```
+
 The transformation will be applied to every row in the specified table. You can limit that to just rows that match a ``WHERE`` clause using ``--where``::
 
     $ sqlite-utils convert content.db articles headline 'value.upper()' \

sqlite_utils/cli.py

@@ -2038,6 +2038,8 @@ def _generate_convert_help():
 
     "value" is a variable with the column value to be converted.
 
+    Use "-" for CODE to read Python code from standard input.
+
     The following common operations are available as recipe functions:
     """
     ).strip()
@@ -2120,6 +2122,9 @@ def convert(
         raise click.ClickException("Cannot use --multi with more than one column")
     if drop and not (output or multi):
         raise click.ClickException("--drop can only be used with --output or --multi")
+    if code == "-":
+        # Read code from standard input
+        code = sys.stdin.read()
     # If single line and no 'return', add the return
     if "\n" not in code and not code.strip().startswith("return "):
         code = "return {}".format(code)

tests/test_cli_convert.py

@@ -515,3 +515,36 @@ def test_convert_where_multi(fresh_db_and_path):
         {"id": 1, "name": "Cleo", "upper": None},
         {"id": 2, "name": "Bants", "upper": "BANTS"},
     ]
+
+
+def test_convert_code_standard_input(fresh_db_and_path):
+    db, db_path = fresh_db_and_path
+    db["names"].insert_all([{"id": 1, "name": "Cleo"}], pk="id")
+    result = CliRunner().invoke(
+        cli.cli,
+        [
+            "convert",
+            db_path,
+            "names",
+            "name",
+            "-",
+        ],
+        input="value.upper()",
+    )
+    assert 0 == result.exit_code, result.output
+    assert list(db["names"].rows) == [
+        {"id": 1, "name": "CLEO"},
+    ]
+
+
+def test_convert_hyphen_workaround(fresh_db_and_path):
+    db, db_path = fresh_db_and_path
+    db["names"].insert_all([{"id": 1, "name": "Cleo"}], pk="id")
+    result = CliRunner().invoke(
+        cli.cli,
+        ["convert", db_path, "names", "name", '"-"'],
+    )
+    assert 0 == result.exit_code, result.output
+    assert list(db["names"].rows) == [
+        {"id": 1, "name": "-"},
+    ]