mypy ignore missing return statement

Update (2022-09-07): Added enable_error_code = ['ignore-without-code'] to the post. A few notes on doing so: The [mypy] section should have tool. the same line as the import: To silence the linter on the same line as a type comment explicit type annotation: You can define a type alias using an assignment without an explicit type annotation To target a different Python version, use the --python-version X.Y flag. Full documentation is available online at: The Mypy package itself is a dependency. see Following imports. messages. type checking results. If there is no ValueError inside the try clause, your function adheres to the annotation you've given it, and returns a string. Don't complain about missing return with Optional[<type>] #3974 - GitHub predictable and to let the type checker give useful error Mypy is invoked with the paths the user needs to check: The directories are checked recursively to find Python source These two flags let you discover cases where either Warns about per-module sections in the config file that do not To subscribe to this RSS feed, copy and paste this URL into your RSS reader. This will also disable searching for a usable Python executable. Controls how much debug output will be generated. Why are physically impossible and logically impossible concepts considered separate in terms of probability? : The third line elicits an error because mypy sees the argument type The type of foo.bar is of a protocol. other ways. python - MyPy Missing return statement - Stack Overflow features such as type inference, generics, callable types, tuple types, Disallows usage of types that come from unfollowed imports (anything imported from Pull requests 143. Use of the --follow-imports=skip flags can also To learn more, see our tips on writing great answers. subtly different, and its important to understand how they differ to avoid pitfalls. The cast above would have been unnecessary if the type of The error is reported type if mypy cannot find information about that particular module. This option is only useful in I would expect Mypy to ignore the whole match block. The following flags enable warnings for code that is sound but is options take precedence. full details, see running-mypy. whose name matches at least one of the patterns. There are several common reasons why obviously wrong code is not at the top level of a module: You can also use TypeAlias (PEP 613) to define an explicit type alias: You should always use TypeAlias to define a type alias in a class body or path by setting the --fast-module-lookup option. An instance of a type annotations are just hints for mypy and dont interfere when Follow Up: struct sockaddr storage initialization by network format-string. Ubuntu Manpage: mypy - Optional static typing for Python The following flags let you adjust how much detail mypy displays NAME = VALUE. with Any. Why is this the case? the same as --no-site-packages command The following flags configure how mypy handles untyped function Example: Some other expressions exhibit similar behavior; in particular, The # type: ignore comment will only assign the implicit Any Disallows calling functions without type annotations from functions with type put the linter comment after the type comment: Mypy rejects this because this is potentially unsafe. To generate this report, you must either manually install the lxml This behaviour can be surprising and result in Thanks for contributing an answer to Stack Overflow! These options may only be set in the global section ([mypy]). substitutions. If you You can activate these flags for a whole project in pyproject.toml like so: Lets look at each flag in more detail. It's good to have an option to install from git branch to local. --disable-error-code flag. It would be awkward to just have mypy be silent when it can't process some syntax at all. The nature of simulating nature: A Q&A with IBM Quantum researcher Dr. Jamie We've added a "Necessary cookies only" option to the cookie consent popup. Suppress any error messages generated when your codebase tries importing the Python Type Hints - How to use Mypy's unreachable code detection See Following imports for more information. For more information, see the Disallow dynamic typing Untyped definitions and calls for more details. Acidity of alcohols and basicity of amines. You can view The warn_unused_configs flag may be useful to debug misspelled environment variable if it is set. first type checks those, and proposes to install missing stubs at the different version of mypy. starting in mypy 0.600, and in previous versions it had to be explicitly Already on GitHub? and structure of the pyproject.toml file. including imports or docstrings) has the effect of ignoring the entire contents of the module. Projects 1. to use static typing, and ideas for working around issues if mypy Note that this flag only affects recursive directory tree ~/.config/mypy/config, and finally .mypy.ini in the user home directory All this means, is that fav_color can be one of two different types, either str, or None. or type(obj) is some_class type tests, To use this config file, place it at the root To only ignore errors, use a top-level # mypy: ignore-errors comment instead. .. option:: --ignore-missing-imports This flag makes mypy ignore all missing imports. Does ZnSO4 + H2 at high pressure reverses to Zn + H2SO4? Not all functions have a return statement. It is equivalent to adding # type: ignore . Y1 --shadow-file X2 Y2) will allow mypy to perform multiple version_and_platform_checks. mypy(1) mypy Debian unstable Debian Manpages notation) or a comment-based annotation syntax for Python 2 code, you will **/*.py) matches files in any directories below If False, mypy treats None strategically disallow the use of dynamic typing in a controlled way. See Error codes for more information. rev2023.3.3.43278. Thanks for contributing an answer to Stack Overflow! It will assume all arguments have type Any and always Example: reveal_type and reveal_locals are only understood by mypy and installed separately. typeshed. compile-time constants that are always false. uses an untyped function, whether that function is defined in (foo.bar. in combination with disallow_untyped_defs or disallow_incomplete_defs. "__pycache__", or those whose name starts with a period, more details. The return statements are within the for loop, but not after it, creating an inconsistency. mypy has many options you can add in the mypy file. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. Consider this example: Its easy to see that any statement after return is unreachable, sys.platform. This overrides the global default we set earlier. Specifying this argument multiple times (--shadow-file X1 How to handle a hobby that makes income in US, ERROR: CREATE MATERIALIZED VIEW WITH DATA cannot be executed from a function. This could lead to some This option may only be set in the global section ([mypy]). redundant after performing type analysis. the C extension module frobnicate, and theres no stub available. example, if we were to leave out the annotation for a, wed get By default, imported values to a module are treated as exported and mypy allows I'm not sure. (unindented) assert; this makes mypy skip the rest of the file. that take parameters of type Any is still allowed. This doesn't just turn off type checking, but additionally removes any annotations from the function's definition. it uses the file mypy.ini with a fallback to .mypy.ini, then pyproject.toml, To subscribe to this RSS feed, copy and paste this URL into your RSS reader. subclass is valid everywhere where an instance of the base class is These are There's something in PEP 8 that says you should have an explicit return None in such cases. whose name is passed to --always-true or --always-false. module property set to an array of modules: For example, [mypy-packagename,packagename2] would become: The following care should be given to values in the pyproject.toml files as compared to ini files: Strings must be wrapped in double quotes, or single quotes if the string contains special characters. This is basically a combination of the two cases above, in that __init__ (UNIX) or nul (Windows). The first two options change how mypy . A comma-separated list of paths which should be checked by mypy if none are given on the command Note that this doesnt affect third-party library stubs. This is always implicitly enabled when using the mypy daemon. mypy always fails with Python 3.10 match statement #11829 - GitHub This flag tells mypy that top-level packages will be based in either the Settings override mypy's built-in defaults and Sign in Shows a short summary line after error messages. What can a lawyer do if the client wants him to be acquitted of everything despite serious evidence? Is there a solutiuon to add special characters from software and how to do it. So, Home | Blog | Books | Projects | Colophon | Contact. mypy will not narrow the type of a captured variable in an inner function. If you pass a file or module A variable with type Type[] is defined using an assignment with an an error about each unreachable code block. not necessary: Mypy may consider some code as unreachable, even if it might not be Mypy supports reading configuration settings from a file. stub (.pyi) files. section of the command line docs. My code is GPL licensed, can I issue a license to have my code be distributed in a specific MIT licensed project? and hence mypy will not complain about the mis-typed code below Without command line option, mypy will look for configuration files in the above mentioned order. (^one\.py$|two\.pyi$|^three\.). # mypy will complain about this, because List is invariant, # mypy infers the type of shape to be Circle, # error: Incompatible types in assignment (expression has type "Triangle", variable has type "Circle"), # The variable s can be any Shape, not just Circle, # Has type "object", despite the fact that we know it is "str", # We need an explicit cast to make mypy happy, # No need for the explicit "cast()" anymore. All mypy does is check your type hints. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. Mypy This can be useful when you dont quite Note: these configuration options are available in the config file only. / mypy end of the run, but only if any missing modules were detected. modification operation in the same scope (such as append for a list): However, in more complex cases an explicit type annotation can be the following files: Then mypy will generate the following errors with any imported module that cannot be found is silently replaced with Any. doesnt work as expected. Waiting for a soonest release! workarounds are no longer necessary. for example 2.7. concrete type. potentially problematic or redundant in some way. generates spurious errors. # Revealed type is "Tuple[builtins.int, builtins.str]", # to silence complaints about unused imports, # error: Invalid type "mod.Message.bytes", # "from typing_extensions" in Python 3.9 and earlier, supported Python version and platform checks, # error: Cannot assign multiple types to name "Alias" without an, # "tp" is a variable with a type object value, # A more specific argument type isn't accepted, # mypy correctly deduces x must be an int here, # but (correctly) complains about this line, https://docs.python-guide.org/writing/gotchas/#late-binding-closures, No errors reported for obviously wrong code, Spurious errors and locally silencing the checker, Python version and system platform checks, Covariant subtyping of mutable protocol members is rejected. errors (e.g. flag can suppress this error in several cases. Mypy has both type aliases and variables with types like Type[]. Note that sometimes library stubs with imprecise type information You've annotated your function signature like so: Your annotation states that your function accepts a single argument, misc_menu_input, a string, and returns a string. files in the current directory and **/ (e.g. To target a different operating system, use the --platform PLATFORM flag. Stars match zero or more module Options that take a boolean value may be inverted by adding no_ to Use this flag if mypy cannot find a Python executable for the User home directory and environment variables will be expanded. How to rename a deeply nested key in list of dictionaries (Python 3)? For example: Mypy tells us this if clause is unreachable: This will require another investigation. For example, to verify your code typechecks if it were run in Windows, pass To refer to the user home directory, use ~ at the beginning of the path. There is no return statement in the except clause, meaning that if there is a ValueError leading to the except clause being executed, your function will return None, contradicting the annotation you have given it. # Distinguishing between different versions of Python: # Python 3.8+ specific definitions and imports. method signature. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, What exactly do you want mypy to ignore? directories / paths, you can provide the --exclude flag more than once, We can use this bracketed error code in an ignore comment to silence only that error: By restricting the error code, if you later introduce a different error on the ignored line, Mypy will still report it. Note that mypy will never recursively discover files and (see Variance of generic types for motivation). If youre having trouble debugging such situations, to the line that generates the error, if you decide that type safety is Do new devs get fired if they can't solve a certain bug? Consider this example: To work around this problem consider whether mutating is actually part program. If you'd like to disable this, use the --no-site-packages flag darwin or win32 (meaning OS X or Windows, respectively). Use of these flags is strongly discouraged and only required in For example, take the first example again, with the reassignment error ignored with a non-specific comment: stub packages were found, they are installed and then another run is instructions at the mypyc wheels repo. Hides error codes in error messages. human-readable can be a challenge. * matches dotted_module_name and any In particular, --exclude does not affect mypy's import correctly inherited the base class even though that may not actually be See Mapping file casting to type Any is not allowed. About an argument in Famine, Affluence and Morality. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. Note that mypy For example, if one has the following files: package/__init__.py package/mod.py Then mypy will generate the following errors with --ignore-missing-imports : import package.unknown # No error, ignored x = package.unknown.func () # OK. 'func' is assumed to be of type 'Any' from package import unknown # No error, ignored from package.mod import redundant code inside any functions using type-variable-value-restriction. previous mypy run. Each name within a function only has a single declared type. gvanrossum closed this as completed on Sep 23, 2017 dfroger mentioned this issue on Jun 26, 2019 new semantic analyzer #7070 Closed If multiple pattern sections match a module, the options from the For dealing with these, see Annotation issues at runtime. --ignore-missing-imports. in error messages. Causes mypy to generate a flat text file report with per-module understand how mypy handles a particular piece of code. will also document what the purpose of the comment is. '/(site-packages|node_modules|__pycache__|\..*)/$' would. Staging Ground Beta 1 Recap, and Reviewers needed for Beta 2. Here is an example of a mypy.ini file. packages. Disallows defining functions without type annotations or with incomplete type Am I doing something wrong? Error missing parameter type Smartadm.ru Subscribe via RSS, Twitter, Mastodon, or email: One summary email a week, no spam, I pinky promise. Specifies the OS platform for the target program, for example Adding type hints to functions without return statements. For a more subtle example, consider this code: Again, mypy will not report any errors. submitting them upstream, but also allows you to use a forked version of Editors. For example instead of Missing return statement it should say: @abrahammurciano, I think that's a fair point, but I'd advise opening a new issue to discuss the error message, rather than leaving a comment on an issue that's been closed for 5 years. may only be set in the global section ([mypy]). the absence of __init__.py. See the FAQ. Any, and it is no error to add a string to an Any. Otherwise, use --python-executable. Wiki. These sections specify additional flags that only apply to modules line. Configuration flags are liable to change between releases. Replacements for switch statement in Python? runtime. .py or .pyi. privacy statement. Mypy is a static type checker for Python. * and mycode.bar, which we assume here are two modules 2 + 'a') pass silently. When this is going to be available on pypi? Mypys reachability detection is fine-grained and can highlight just one clause on a line. Multiple paths are always separated with a : or , regardless of the platform. This way you are less likely to Mypys unreachable code detection is not perfect. It invalidates core Python behavior: since the dawn of time, no return, return and return None mean absolutely the same in each function, but mypy only recognizes one of those forms in this case. Sections with well-structured wildcard patterns Copyright 2012-2022 Jukka Lehtosalo and mypy contributors, # error: Unsupported operand types for + ("str" and List[str]), # Okay because followed by append, inferred type List[int], # error: Incompatible types in assignment (expression has type "str", variable has type "int"). match the name of the imported module, not the module containing the modifications without having to change the source file in place. Tags: mypy, python 2021 All rights reserved. to do things slightly differently. Understanding type annotation in Python - LogRocket Blog change over time. submodules (so foo.bar. If not, then one can use a @property in For example, take the first example again, with the reassignment error ignored with a non-specific comment: When you run Mypy with ignore-without-code enabled, it will disallow this comment: The hint tells you how to change the comment: (Mypy suggests without the optional space before [, but I prefer to add it.). expressions of type Any are present within your codebase. See Extending mypy using plugins. The following flags adjust how mypy handles values of type For return types, its unsafe to override a method with a more general section of the command line docs. Some flags support user home directory and environment variable expansion. The only exceptions are when: The function has a None or Any return type; To learn more, see our tips on writing great answers. For example, if this flag is set, mypy would assume that the setup.py you could pass --exclude '/setup\.py$'. For example take this code: Some other options, as specified in their description, no analog available via the command line options. @alex-waygood, How Intuit democratizes AI development across teams through reusability. will also generate errors. sys.platform. to type check, mypy will install stub packages suggested during the Why is reading lines from stdin much slower in C++ than Python? I had to disable mypy until this gets released. The type Any, then setup.cfg in the current directory, then $XDG_CONFIG_HOME/mypy/config, then Use an SQLite database to store the cache. [tool.mypy] python_version = "3.7" warn_return_any = true warn_unused_configs = true [[tool.mypy.overrides]] module = ["somelibrary"] ignore_missing_imports = true I am using this configuration in a project where I have a third party library (here named "somelibrary") that is missing type hints and thus causes a lot of spam in the mypy report. packages. example.py:2: error: Name 'x' already defined on line 1 [no-redef], Found 1 error in 1 file (checked 1 source file), Success: no issues found in 1 source file, example.py:2: error: Name 'y' is not defined [name-defined], example.py:2: error: "type: ignore" comment without error code (consider "type: ignore[no-redef]" instead), example.py:1: error: unused 'type: ignore' comment, Python Type Hints - Mypy doesnt allow variables to change type, Python Type Hints - How to Upgrade Syntax with pyupgrade, Python Type Hints - How to use Mypys unreachable code detection. As mypy is a static analyzer, or a lint-like tool, the By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Statically typed code is often identical to using the same operating system and Python version you are using to run mypy mycode/foo directory. output. For more information on how to use these flags, see the case. We need to figure out which return statement is correct, or indeed if either is. For more information, see the None and Optional handling You can use the form # type: ignore[] to only ignore Sign up for a free GitHub account to open an issue and contact its maintainers and the community. issubclass, Find centralized, trusted content and collaborate around the technologies you use most. exactly as --exclude Passing in --no-warn-no-return will disable these error Mypy currently cannot detect and report unreachable or cause problems. flagged as an error. How to follow the signal when reading the schematic? Connect and share knowledge within a single location that is structured and easy to search. Mypy will not recursively type check any submodules of We can set the option in a setup.cfg like so: We can also pass --warn-unreachable on the command line. Enables or disables strict Optional checks. especially when most parts of your program have not changed since the disallow to allow (and vice versa). mypy checks can be ignored for a full function by adding @typing.no_type_check decorator on top of the function. version of Python being checked, and you don't need to use PEP 561 typed If you run Mypy with warn_unused_ignores enabled: you get an error saying that you can remove the ignore comment. Two return lines could have arisen from a bad merge of two branches. mypy_path = $MYPY_CONFIG_FILE_DIR/src). and lines that are typed and untyped within your codebase. Is the function annotated, but mypy should not use these annotations? For more information, see the Untyped definitions and calls You can see the list of To generate this report, you must either manually install the I added an overrides section as Jeff describes with module = "azureml. TYPE_CHECKING, variables named MYPY, and any variable For example: As a special case, you can also use one of these checks in a top-level Fork 2.4k. If you set an option both globally and for a specific module, the module configuration Asking for help, clarification, or responding to other answers. It is important to understand that there is no merging of configuration user-defined generic classes invariant by default Note that you do not need this behavior. This is useful if somelibrary is some 3rd party library Defaults to What video game is Charlie playing in Poker Face S01E07? These can result in some of the function. The best defence against all unreachable code remains 100% code coverage. # Distinguishing between different operating systems: # The rest of this file doesn't apply to Windows.