Python 如何在具有匹配字符串的嵌套列表中查找索引的最小值和最大值？

我有一个包含潮汐数据的文本文件，前几行是：

1月4日星期四，11.58,0.38米

1月4日星期四，16.95,0.73米

1月4日星期四，23.68,0.02米

1月5日星期五，6.48，0.83米

1月5日星期五，12.42,0.33米

等，并持续5天以上的数据

我已将此数据转换为嵌套列表，因此它现在打印为：

[['Thursday 4 January', 11.58, 0.38], ['Thursday 4 January', 16.95, 0.73], ['Thursday 4 January', 23.68, 0.02], ['Friday 5 January', 6.48, 0.83], ['Friday 5 January', 12.42, 0.33].....]

以此类推，对于文件中的每一行数据，每个列表的第一个索引是字符串中的日期，第二个和第三个索引是浮动的

对于当天具有匹配[0]索引的每个嵌套列表，我需要找到每个匹配嵌套列表的最低和最高浮动[2]索引潮汐高度，并将其打印到每天的屏幕上

例如：

Thursday 4 January: 0.02 meters at lowest and 0.73 meters at highest
Friday 5 January: 0.33 meters at lowest and 0.83 meters at highest

由于列表已按天排序，我想只计算匹配的名称，然后手动比较，例如“1月4日星期四”，因为有3个，我只需比较split_tides[0-2][2]，找到最小值和最大值，然后每天重复。但我认为一定有一种方法可以自动比较具有匹配字符串的嵌套列表

谢谢你的帮助

编辑：文本文件的图像

首先，您可以使用groupby按日期分组，并按第三个索引高度排序。此处的示例代码：

    from itertools import groupby
    from operator import itemgetter

    data = [['Thursday 4 January', 11.58, 0.38], ['Thursday 4 January', 16.95, 0.73], ['Thursday 4 January', 23.68, 0.02],
         ['Friday 5 January', 6.48, 0.83], ['Friday 5 January', 12.42, 0.33]]

    for k, g in groupby(data, key=itemgetter(0)):
        a = sorted(g, key=itemgetter(2))
        print('{}: {} meters at lowest and {} meters at highest'.format(k, a[0][2], a[-1][2]))

输出：

Thursday 4 January: 0.02 meters at lowest and 0.73 meters at highest
Friday 5 January: 0.33 meters at lowest and 0.83 meters at highest

顺便说一下，在日期中使用groupby之前，请确保您的数据按日期排序

希望这将对您有所帮助，如果您还有其他问题，请发表评论：

首先，您可以使用groupby按日期分组，并按第三个索引高度排序。此处的示例代码：

    from itertools import groupby
    from operator import itemgetter

    data = [['Thursday 4 January', 11.58, 0.38], ['Thursday 4 January', 16.95, 0.73], ['Thursday 4 January', 23.68, 0.02],
         ['Friday 5 January', 6.48, 0.83], ['Friday 5 January', 12.42, 0.33]]

    for k, g in groupby(data, key=itemgetter(0)):
        a = sorted(g, key=itemgetter(2))
        print('{}: {} meters at lowest and {} meters at highest'.format(k, a[0][2], a[-1][2]))

data = [['Thursday 4 January', 11.58, 0.38], ['Thursday 4 January', 16.95, 0.73], ['Thursday 4 January', 23.68, 0.02], ['Friday 5 January', 6.48, 0.83], ['Friday 5 January', 12.42, 0.33]]

dic={'day':[],'min':[],'max':[]}
for i in data :
    dic['day']+=[i[0]]
    dic['min']+=[i[1]]
    dic['max']+=[i[2]]



from collections import defaultdict
x = defaultdict(dict)

for i in dic['day']:
    x[i]={'min':[],'max':[]}

for i in range(len(dic['min'])):
    x[dic['day'][i]]['min']+=[dic['min'][i]]
    x[dic['day'][i]]['max']+=[dic['max'][i]]

print(dict(x))
"""
structure data for future use

{'Friday 5 January': {'max': [0.83, 0.33], 'min': [6.48, 12.42]},
 'Thursday 4 January': {'max': [0.38, 0.73, 0.02],
  'min': [11.58, 16.95, 23.68]}}
"""



result =[]
for i in x:
    result.append(r'{}: {} meters at lowest an {} meters at highest'.format(i,min(x[i]['min']),max(x[i]['max'])))


print(result)

"""output

['Thursday 4 January: 11.58 meters at lowest an 0.73 meters at highest', 'Friday 5 January: 6.48 meters at lowest an 0.83 meters at highest']
""""

输出：

Thursday 4 January: 0.02 meters at lowest and 0.73 meters at highest
Friday 5 January: 0.33 meters at lowest and 0.83 meters at highest

顺便说一下，在日期中使用groupby之前，请确保您的数据按日期排序

---

希望这将对您有所帮助，如果您还有其他问题，请发表评论：

下面是可以帮助您的代码片段

data = [['Thursday 4 January', 11.58, 0.38], ['Thursday 4 January', 16.95, 0.73], ['Thursday 4 January', 23.68, 0.02], ['Friday 5 January', 6.48, 0.83], ['Friday 5 January', 12.42, 0.33]]

dic={'day':[],'min':[],'max':[]}
for i in data :
    dic['day']+=[i[0]]
    dic['min']+=[i[1]]
    dic['max']+=[i[2]]



from collections import defaultdict
x = defaultdict(dict)

for i in dic['day']:
    x[i]={'min':[],'max':[]}

for i in range(len(dic['min'])):
    x[dic['day'][i]]['min']+=[dic['min'][i]]
    x[dic['day'][i]]['max']+=[dic['max'][i]]

print(dict(x))
"""
structure data for future use

{'Friday 5 January': {'max': [0.83, 0.33], 'min': [6.48, 12.42]},
 'Thursday 4 January': {'max': [0.38, 0.73, 0.02],
  'min': [11.58, 16.95, 23.68]}}
"""



result =[]
for i in x:
    result.append(r'{}: {} meters at lowest an {} meters at highest'.format(i,min(x[i]['min']),max(x[i]['max'])))


print(result)

"""output

['Thursday 4 January: 11.58 meters at lowest an 0.73 meters at highest', 'Friday 5 January: 6.48 meters at lowest an 0.83 meters at highest']
""""

from pandas import DataFrame

data = [['Thursday 4 January', 11.58, 0.38], ['Thursday 4 January', 16.95, 0.73], ['Thursday 4 January', 23.68, 0.02],
         ['Friday 5 January', 6.48, 0.83], ['Friday 5 January', 12.42, 0.33]]

df = DataFrame.from_records(data)

df.columns = ["Date", "Value", "Height"]

df.groupby(['Date'])['Height'].max()
df.groupby(['Date'])['Height'].min()

输出：

日期 1月5日星期五0时83分 1月4日星期四0时73分

日期 1月5日星期五0时33分

---

0.02年1月4日星期四

以下是对您有帮助的片段

from pandas import DataFrame

data = [['Thursday 4 January', 11.58, 0.38], ['Thursday 4 January', 16.95, 0.73], ['Thursday 4 January', 23.68, 0.02],
         ['Friday 5 January', 6.48, 0.83], ['Friday 5 January', 12.42, 0.33]]

df = DataFrame.from_records(data)

df.columns = ["Date", "Value", "Height"]

df.groupby(['Date'])['Height'].max()
df.groupby(['Date'])['Height'].min()

输出：

日期 1月5日星期五0时83分 1月4日星期四0时73分

日期 1月5日星期五0时33分

---

0.02年1月4日星期四

你能保证某一天的结果总是在一起吗？@Austin是的，如果你是这个意思的话，这些天总是井然有序的，而且是组合在一起的。我将把这个文本文件添加到我的问题中。你能保证某一天的结果总是在一起吗？@Austin是的，如果你是这个意思的话，这些天总是按顺序分组的。我将把文本文件添加到我的问题中。