LINQ 的 Python 等效项

在 C# 中，使用 LINQ，如果我有 en 枚举enumerable， 我可以：

// a: Does the enumerable contain an item that satisfies the lambda?
bool contains = enumerable.Any(lambda);

// b: How many items satisfy the lambda?
int count = enumerable.Count(lambda);

// c: Return an enumerable that contains only distinct elements according to my custom comparer
var distinct = enumerable.Distinct(comparer);

// d: Return the first element that satisfies the lambda, or throws an exception if none
var element = enumerable.First(lambda);

// e: Returns an enumerable containing all the elements except those
// that are also in 'other', equality being defined by my comparer
var except = enumerable.Except(other, comparer);

我听说 Python 的语法比 C# 更简洁（因此效率更高），那么如何使用 Python 中的可迭代对象以相同或更少的代码实现相同的效果？

注意：如果不需要的话，我不想将可迭代物化为列表（Any, Count, First).

以下 Python 行应该与您所拥有的相同（假设func, or lambda在您的代码中，返回一个布尔值）：

# Any
contains = any(func(x) for x in enumerable)

# Count
count = sum(func(x) for x in enumerable)

# Distinct: since we are using a custom comparer here, we need a loop to keep 
# track of what has been seen already
distinct = []
seen = set()
for x in enumerable:
    comp = comparer(x)
    if not comp in seen:
        seen.add(comp)
        distinct.append(x)

# First
element = next(iter(enumerable))

# Except
except_ = [x for x in enumerable if not comparer(x) in other]

参考：

• 列表推导式 http://docs.python.org/tutorial/datastructures.html#list-comprehensions
• 生成器表达式 http://docs.python.org/tutorial/classes.html#generator-expressions
• any()内置功能 http://docs.python.org/library/functions.html#any
• sum()内置功能 http://docs.python.org/library/functions.html#sum
• set type http://docs.python.org/library/stdtypes.html#set-types-set-frozenset

注意我改名了lambda to func since lambda是Python中的一个关键字，我重命名为except to except_为了同样的原因。

请注意，您还可以使用map() http://docs.python.org/library/functions.html#map而不是推导式/生成器，但它通常被认为可读性较差。