i.e. In Python 3.x, the reduce function already explained here has been removed from the built-ins and must now be imported from functools. Note: The article is based on Python 3.8.2 (CPython). In Python 3, however, the function returns a map object which is a generator object. To get the result as a list, the built-in list() function can be called on the map object. reduce() 函数在 python 2 是内置函数, 从python 3 开始移到了 functools 模块。 官方文档是这样介绍的 reduce (…) reduce (function, sequence[, initial]) -> value Apply a function of two arguments cumulatively to the items of Under Python 2, classes could define a __cmp__() ... $ python3 functools_reduce_initializer.py range(1, 5) do_reduce(99, 1) do_reduce(100, 2) do_reduce(102, 3) do_reduce(105, 4) result: 109 Sequences with a single item automatically reduce to that value when no initializer is present. For example, if you wanted to compute the product of a list of integers. Reduce¶ Reduce is a really useful function for performing some computation on a list and returning the result. list(map(func, *iterables)) The number of arguments to func … You can find the code snippets used in the article on GitHub. It can save time when an expensive or I/O bound function is periodically called with the same arguments. In Python 2, the map() function retuns a list. In general, any callable object can be treated as a function for the purposes of this module. The functools module is for higher-order functions: functions that act on or return other functions. Guido: “I value readability and usefulness for real code. reduce() singledispatch() singledispatchmethod() total_ordering() update_wrapper() wraps() Throughout the article, we will have a closer look at each function and a few examples where they are useful. Tried this: xor = lambda x,y: (x+y)%2 l = reduce(xor, [1,2,3,4]) And got the following error: l = reduce(xor, [1,2,3,4]) NameError: name 'reduce' is not defined Tried printing reduce into interactive console - got this error: NameError: name 'reduce' is not defined Is reduce really removed in Python 3.2? The functools module is for higher-order functions: functions that act on or return other functions. Enjoy! The functools module defines the following functions:. from functools import reduce def factorial (n): return reduce (lambda a, b: (a * … I'm using Python 3.2. @functools.lru_cache(maxsize=128, typed=False)¶ Decorator to wrap a function with a memoizing callable that saves up to the maxsize most recent calls. 3.2 新版功能. 4.3. Python’s creator, Guido van Rossum, doesn’t like functional programming a lot. # reduce. Note: The total_ordering function is only available since Python 2.7. It applies a rolling computation to sequential pairs of values in a list. 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