.. _implicit-str-concat:

implicit-str-concat / W1404
===========================

**Message emitted:**

``Implicit string concatenation found in %s``

**Description:**

*String literals are implicitly concatenated in a literal iterable definition : maybe a comma is missing ?*

**Problematic code:**

``list.py``:

.. literalinclude:: /data/messages/i/implicit-str-concat/bad/list.py
    :language: python


``open.py``:

.. literalinclude:: /data/messages/i/implicit-str-concat/bad/open.py
    :language: python


**Correct code:**

``list.py``:

.. literalinclude:: /data/messages/i/implicit-str-concat/good/list.py
    :language: python


``open.py``:

.. literalinclude:: /data/messages/i/implicit-str-concat/good/open.py
    :language: python



**Additional details:**

By default, detection of implicit string concatenation of line jumps is disabled.
Hence the following code will not trigger this rule:

.. code-block:: python

    SEQ = ('a', 'b'
                'c')

In order to detect this case, you must enable `check-str-concat-over-line-jumps`:

.. code-block:: toml

    [STRING_CONSTANT]
    check-str-concat-over-line-jumps = true

However, the drawback of this setting is that it will trigger false positive
for string parameters passed on multiple lines in function calls:

.. code-block:: python

    warnings.warn(
        "rotate() is deprecated and will be removed in a future release. "
        "Use the rotation() context manager instead.",
        DeprecationWarning,
        stacklevel=3,
    )

No message will be emitted, though, if you clarify the wanted concatenation with parentheses:

.. code-block:: python

    warnings.warn(
        (
            "rotate() is deprecated and will be removed in a future release. "
            "Use the rotation() context manager instead."
        ),
        DeprecationWarning,
        stacklevel=3,
    )



Created by the `string <https://github.com/pylint-dev/pylint/blob/main/pylint/checkers/strings.py>`__ checker.