Python中模拟C# Linq的一些操作

闲来无事时积累的一些Linq函数，有时间就更新。

需要注意python版本如果低于3.0不支持lambda，只能单独写函数传参，比较麻烦

1.FirstOrDefault:

def FirstOrDefault(collection, func):
    result = filter(func, collection)
    
    if len(result) == 0: return None
    
    return result[0]

def main():
    def condition(m): return m < 3
    print FirstOrDefault([1,2,3,4], condition)
    
#print 1

返回1

2.Where:

def Where(collection, func):
    result = filter(func, collection)
    
    if len(result) == 0: return None
    
    return result

def main():
    def condition(m): return m < 3
    print Where([1,2,3,4], condition)
#print [1,2]

 返回筛选后的数组1,2

3.Distinct:

def Distinct(collection, isContainFunc):
    resultList = list()

    for item in collection:
        def firstOrDefaultPredicate(m):
            return isContainFunc(m,item)

        containValue = FirstOrDefault(collection, firstOrDefaultPredicate)
        
        if containValue != None:
            if not item in resultList:
                resultList.append(item)

    return resultList

def main():
    tmp = [1,2,2,3,4,3]
    
    def compare(x,y):return x==y
    result = Distinct(tmp, compare)
    print result
    #print [1,2,3,4]

去重复，依赖FirstOrDefault。