The nicest way to develop a command-line interface
Project description
Coleo
Coleo is a minimum-effort way to create a command-line interface in Python.
- Declare options where they are used.
- Scale easily to extensive CLIs with dozens of subcommands and options.
Basic usage
First, define a command line interface as follows:
from coleo import Argument, auto_cli, default
def main():
# The greeting
greeting: Argument = default("Hello")
# The name to greet
name: Argument = default("you")
return f"{greeting}, {name}!"
if __name__ == "__main__":
auto_cli(main)
Then you may run it like this on the command line:
$ python hello.py
Hello, you!
$ python hello.py --name Luke
Hello, Luke!
$ python hello.py --name Luke --greeting "Happy birthday"
Happy birthday, Luke!
$ python hello.py -h
usage: hello.py [-h] [--greeting VALUE] [--name VALUE]
optional arguments:
-h, --help show this help message and exit
--greeting VALUE The greeting
--name VALUE The name to greet
- Any variable annotated with
Argument
will become an option. - You can provide a default value with
default(value)
, although you don't have to, if the argument is required. - If there is a comment above the variable, it will be used as documentation for the option.
Argument types
By default, all arguments are interpreted as strings, but you can easily give a different type to an argument:
def main():
# This argument will be converted to an int
x: Argument & int
# This argument will be converted to a float
y: Argument & float
return x + y
Boolean flags
If the type is bool, the option will take no argument, and the --no-<optname>
option is added to negate the value. For example:
def main():
flag: Argument & bool
return "yes!" if flag else "no!"
Use it like this:
$ python script.py --flag
yes!
$ python script.py --no-flag
no!
Files
Use coleo.FileType
(or argparse.FileType
, it's the same thing) to open a file to read from or to write to:
def main():
grocery_list: Argument & coleo.FileType("r")
with grocery_list as f:
for food in f.readlines():
print(f"Gotta buy some {food}")
Config
You can manipulate configuration files with coleo.config
or coleo.ConfigFile
:
def main():
# ConfigFile lets you read or write a configuration file
book: Argument & ConfigFile
contents = book.read()
contents["xyz"] = "abc"
book.write(contents)
# config will read the file for you or parse the argument as JSON
magazine: Argument & config
print(magazine)
Use it simply like this:
$ python librarian.py --book alice.json --magazine vogue.json
$ python librarian.py --book history.yaml --magazine gamez.toml
$ python librarian.py --book physics.json --magazine '{"a": 1, "b": 2}'
# etc
Supported extensions are json
, yaml
and toml
(the latter two require installing the pyyaml
or toml
packages).
Other
Any function can be used as a "type" for an argument. So for example, if you want to be able to provide lists and dictionaries on the command line you can simply use json.loads
(although coleo.config
is usually better, because it can also read files, in various formats):
def main():
obj: Argument & json.loads
return type(obj).__name__
$ python json.py --obj 1
int
$ python json.py --obj '"hello"'
str
$ python json.py --obj '{"a": 1, "b": 2}'
dict
If you're feeling super feisty and care nothing about safety, you can even use eval
:
def main():
obj: Argument & eval
return type(obj).__name__
$ python eval.py --obj "1 + 2"
int
$ python eval.py --obj "lambda x: x + 1"
function
Customization
Using comments of the form # [<instruction>: <args ...>]
you can customize the option parser:
def main():
# This argument can be given as either --greeting or -g
# [alias: -g]
greeting: Argument = default("Hello")
# This argument is positional
# [positional]
name: Argument = default("you")
# This argument can only be given as -n
# [options: -n]
ntimes: Argument & int = default(1)
for i in range(ntimes):
print(f"{greeting}, {name}!")
The above would be used like this:
$ python hello.py Alice -g Greetings -n 2
Greetings, Alice!
Greetings, Alice!
The following customizations are available:
[alias: ...]
defines one or several options that are aliases for the main one. Options are separated by spaces, commas or semicolons.[options: ...]
defines one or several options for this argument, which override the default one. Options are separated by spaces, commas or semicolons.[positional]
defines one positional argument.[positional: n]
: n positional arguments (a list is returned).[positional: ?]
: one optional positional argument[positional: *]
: zero or more positional arguments[positional: +]
: one or more positional arguments
It is currently not possible to define multiple arguments as positional, although you can simulate it by using e.g. [positional: 2]
on a single argument to get a pair, and then you can get the elements of the list.
Subcommands
You can create an interface with a hierarchy of subcommands by passing a dictionary to auto_cli
:
def add():
x: Argument & int
y: Argument & int
return x + y
def mul():
x: Argument & int
y: Argument & int
return x * y
def pow():
base: Argument & int
exponent: Argument & int
return base ** exponent
def greet():
greeting: Argument = default("Hello")
name: Argument = default("you")
return f"{greeting}, {name}!"
if __name__ == "__main__":
auto_cli({
"calc": {
"__doc__": "Calculate something!",
"add": add,
"mul": mul,
"pow": pow,
},
"greet": greet,
})
Then you may use it like this:
$ python multi.py greet --name Alice --greeting Hi
Hi, Alice!
$ python multi.py calc add --x=3 --y=8
11
Sharing arguments
It is possible to share behavior and arguments between subcommands, or to split complex functionality into multiple pieces. For example, maybe multiple subcommands in your application require an API key, which can either be given on the command line or can be read from a file. This is how you would share this behavior across all subcommands:
from coleo import Argument, auto_cli, default, tooled
@tooled
def apikey():
# The API key to use
key: Argument = default(None)
if key is None:
# If no key parameter is given on the command line, try to read it from
# some standard location.
key = config("~/.config/myapp/config.json")["key"]
return key
def search():
interface = Application(apikey())
query: Argument
return interface.search(query)
def install():
interface = Application(apikey())
package: Argument
return interface.install(package)
if __name__ == "__main__":
auto_cli({"search": search, "install": install})
If a function is decorated with @tooled
and is called from one of the main functions (or from another tooled function), Coleo will search for arguments in that function too. Thus any subcommand that calls apikey()
will gain a --key
option.
In addition to this, you can "share" arguments by defining the same argument with the same type in multiple functions. Coleo will set all of them to the same value.
For example, in the example above you could easily let the user specify the path to the file that contains the key, simply by replacing
key = config("~/.config/myapp/config.json")["key"]
# ==>
config_path: Argument = default("~/.config/myapp/config.json")
key = config(config_path)["key"]
And that config_path
argument could, of course, be declared in any other function that needs to read some configuration value.
Non-CLI usage
It is possible to set arguments without auto_cli
with setvars
:
from coleo import Argument, setvars, tooled
@tooled
def greet():
greeting: Argument = default("Hello")
name: Argument = default("you")
return f"{greeting} {name}!"
with setvars(greeting="Hi", name="Bob"):
assert greet() == "Hi bob!"
Note:
- With
setvars
, you must decorate the function with@tooled
(this is somethingauto_cli
does on your behalf). setvars
entirely bypasses the option parsing and the type annotations will not be used to wrap these values. In other words, if a variable is annotatedArgument & int
and you provide the value "1", it will remain a string.
Using with Ptera
Coleo is based on Ptera and all of Ptera's functionality is de facto available on functions marked as @tooled
. For example, using the example above:
# Set the variables in the greet function -- it's a bit like making an object
hibob = greet.new(greeting="Hi", name="Bob")
assert hibob() == "Hi Bob!"
# Same as above but this would also change greeting/name in any other function
# that is called by greet, and so on recursively (a bit like dynamic scoping)
hibob = greet.tweaking({"greeting": "Hi", "name": "Bob"})
assert hibob() == "Hi Bob!"
# More complex behavior
from ptera import overlay
with overlay.tweaking({
"greet(greeting='Bonjour') > name": "Toto"
}):
assert greet() == "Hello you!"
assert greet.new(greeting="Hi")() == "Hi you!"
assert greet.new(greeting="Bonjour")() == "Bonjour toto!"
Read the documentation for Ptera for more information. Note that Ptera is not limited to variables tagged Argument
, it can manipulate any variable in a tooled function.
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