mirror of
https://github.com/bazel-contrib/bazel-lib
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138 lines
3.1 KiB
Python
138 lines
3.1 KiB
Python
"Function definitions for working with lists"
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def every(f, arr):
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"""Check if every item of `arr` passes function `f`.
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Example:
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`every(lambda i: i.endswith(".js"), ["app.js", "lib.js"]) // True`
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Args:
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f: Function to execute on every item
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arr: List to iterate over
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Returns:
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True or False
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"""
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return len(filter(f, arr)) == len(arr)
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def filter(f, arr):
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"""Filter a list `arr` by applying a function `f` to each item.
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Example:
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`filter(lambda i: i.endswith(".js"), ["app.ts", "app.js", "lib.ts", "lib.js"]) // ["app.js", "lib.js"]`
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Args:
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f: Function to execute on every item
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arr: List to iterate over
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Returns:
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A new list containing items that passed the filter function.
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"""
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res = []
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for a in arr:
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if f(a):
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res.append(a)
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return res
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def find(f, arr):
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"""Find a particular item from list `arr` by a given function `f`.
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Unlike `pick`, the `find` method returns a tuple of the index and the value of first item passing by `f`.
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Furthermore `find` does not fail if no item passes `f`.
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In this case `(-1, None)` is returned.
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Args:
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f: Function to execute on every item
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arr: List to iterate over
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Returns:
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Tuple (index, item)
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"""
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i = 0
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for a in arr:
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if f(a):
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return (i, a)
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i += 1
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return (-1, None)
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def map(f, arr):
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"""Apply a function `f` with each item of `arr` and return a new list.
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Example:
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`map(lambda i: i*2, [1, 2, 3]) // [2, 4, 6]`
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Args:
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f: Function to execute on every item
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arr: List to iterate over
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Returns:
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A new list with all mapped items.
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"""
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return [f(a) for a in arr]
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def once(f, arr):
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"""Check if exactly one item in list `arr` passes the given function `f`.
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Args:
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f: Function to execute on every item
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arr: List to iterate over
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Returns:
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True or False
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"""
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return len(filter(f, arr)) == 1
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def pick(f, arr):
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"""Pick a particular item in list `arr` by a given function `f`.
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Unlike `filter`, the `pick` method returns the first item _found_ by `f`.
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If no item has passed `f`, the function will _fail_.
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Args:
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f: Function to execute on every item
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arr: List to iterate over
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Returns:
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item
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"""
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for a in arr:
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if f(a):
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return a
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fail("Could not find any item")
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def some(f, arr):
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"""Check if at least one item of `arr` passes function `f`.
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Example:
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`some(lambda i: i.endswith(".js"), ["app.js", "lib.ts"]) // True`
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Args:
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f: Function to execute on every item
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arr: List to iterate over
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Returns:
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True or False
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"""
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for a in arr:
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if f(a):
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return True
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return False
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def unique(arr):
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"""Return a new list with unique items in it.
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Example:
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`unique(["foo", "bar", "foo", "baz"]) // ["foo", "bar", "baz"]`
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Args:
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arr: List to iterate over
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Returns:
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A new list with unique items
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"""
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res = []
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for a in arr:
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if a not in res:
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res.append(a)
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return res
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