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从列表中的元组返回具有流量强度的日期

tuples python-3.x python

user9644895 · 技术社区 · 7 年前

我试图在下面的函数中返回与流量强度匹配的所有日期,但只将第一个元组的所有元素作为列表,而不是所有匹配的元组。

def traffic_intensity(count):
   """Returns string indicating intensity level given by number of 
    vehicles"""
    level_name = ""
    if(count < 5000):
        level_name = "Very Low"
    elif(count >= 5000 and count < 10000):
        level_name = "Low"
    elif(count >= 10000 and count < 18000):
       level_name = "Moderate"
    elif(count >= 18000):
        level_name = "High"
    return(level_name)


def dates_with_intensity(vehicle_records, intensity):
    """Returns number of days with the given traffic intensity level"""
    new_list = []
    for number in vehicle_records:
        date_count = number[0]
        number_count = number[1]
        traffic = traffic_intensity(number_count)
        if traffic == intensity:
            new_list += date_count
        return new_list

对于测试数据

vehicle_records = [('2010-01-01',1),
                ('2010-01-02',2),
                ('2010-01-03',3)]
days = dates_with_intensity(vehicle_records, 'Very Low')
print(days)

我应该

['2010-01-01', '2010-01-02', '2010-01-03']

但相反,我

['2', '0', '1', '0', '-', '0', '1', '-', '0', '1']

谁能帮我一下吗?

2 回复 | 直到 7 年前

Primusa 7 年前

将返回值从for循环中取出。此外,date\u count不是数组,因此您应该使用 .append() 不添加:

def dates_with_intensity(vehicle_records, intensity):
"""Returns number of days with the given traffic intensity level"""
    new_list = []
    for number in vehicle_records:
        date_count = number[0]
        number_count = number[1]
        traffic = traffic_intensity(number_count)
        if traffic == intensity:
            new_list.append(date_count)
    return new_list

Community CDub 4 年前

有两个问题,一个是 return 在里面 for 循环,导致只查看一个项目。另一个是您可能需要扩展阵列 new_list 具有 date_count 。您可以尝试以下操作:

def dates_with_intensity(vehicle_records, intensity):
    """Returns number of days with the given traffic intensity level"""
    new_list = []
    for number in vehicle_records:
        date_count = number[0]
        number_count = number[1]

        traffic = traffic_intensity(number_count)
        if traffic == intensity:
            new_list += [date_count] # extend as array
    return new_list # move return

要测试类似的场景,可以考虑以下示例:

l = []
l += "string"
print(l)

结果:

['s', 't', 'r', 'i', 'n', 'g']

而是:

l = []
l += ["string"]
print(l)

结果:

['string']

关于更多信息,我建议 relevant discussion 。

更新时间:

我认为代码可以短一些 list comprehension 并删除中的条件 elif 包括以下内容:

def traffic_intensity(count):
    """Returns string indicating intensity level given by number of vehicles"""
    if (count < 5000): return "Very Low"
    elif(count < 10000): return "Low"
    elif(count < 18000): return "Moderate"
    else: return "High"
    

def dates_with_intensity(vehicle_records, intensity):
    """Returns number of days with the given traffic intensity level"""
    return [date for date, num in vehicle_records if intensity == traffic_intensity(num)]