如何从python dicts列表创建范围？

Question

I'm using openpyxl to evaluate a worksheet. There is one row on this worksheet contains column_group names in merged cells. i created a list of dicts where column_group is key and column number is value

col_groups= [{u'Layer': 1}, {u'Single Ended': 17},\
             {u'Single Ended': 22}, {u'Edge Coupled': 27}]

now I want to create a group_name:(start_column:end_column) dictionary using col_groups

This is the closest I've been able to get.

group_cols = []
for x, d in enumerate(col_groups):
    try:
        group_cols.append({col_groups[x].keys()[0]:(col_groups[x].values()[0],(col_groups[(x+1)].values()[0] - 1))})
    except:
        group_cols.append({col_groups[x].keys()[0]:(col_groups[x].values()[0],tap_sh.max_column)})

typing group_cols at the python shell prompt gives:

[{u'Layer': (1, 16)}, {u'Single Ended': (17, 21)}, {u'Single Ended': (22, 26)}, {u'Edge Coupled': (27, 33)}]

The output looks ok but my method feels a bit hackish- any suggestions to be more pythonic will be appreciated

Answer 1

A dictionary is the wrong structure, a tuple (name, idx) would be better, for this but you can work with it.

# define a sort key (Python 3 compatible)
def sort_key(value):
    "Sort by the value"
    return list(value.values())[-1]

ordered_groups = []
max_column = 34
for group in sorted(col_groups, key=sort_key, reverse=True):
    key, begin = list(group.items())[0]
    end = max_column - 1
    max_column = begin
    ordered_groups.append((key, (begin, end)))
dict(ordered_groups)

Answer 2

The only time your try statement fails, is when you are at the end of the list, and are trying to access the element after the last element. In such cases using an if statement is probably better.

col_groups = [{u'Layer': 1}, {u'Single Ended': 17},
              {u'Single Ended': 22}, {u'Edge Coupled': 27}]

group_cols = []
for i in range(col_groups):
    key = col_groups[i].keys()[0]
    first_val = col_groups[i].values()[0]
    if i != len(col_groups) - 1:
        second_val = col_groups[i + 1].values()[0] - 1
    else:
        second_val = tap_sh.max_column
    values = (first_val, second_val)
    group_cols.append({key: values})