Python中OrderedDict字符串元素索引结果及指定代码中max_wait_time的取值与运行可行性问询

Hey there! Let's break down your two Python questions one by one:

First off, remember that OrderedDict (from the collections module) is just a dict that preserves insertion order—it behaves almost exactly like a regular Python dictionary in most ways. When you use a string as an index (aka a key) to access an OrderedDict, you'll get the corresponding value tied to that key, just like with a standard dict.

For example:

from collections import OrderedDict
my_od = OrderedDict([('EAF', [1]), ('AOD', [2]), ('LF', [3])])
print(my_od['EAF'])  # Output: [1]
print(my_od['LF'])   # Output: [3]

If you try to index with a string that's not a key in the OrderedDict, you'll get a KeyError—same as a normal dict.

Let's start with the hard truth: this code won't run as-is because of a couple of critical errors. Let's walk through them, then fix the code to explain the logic you're curious about.

First error: Wrong type for rescat2idx #

You defined rescat2idx as a list (wrapped in square brackets, with an extra 174 at the end), but lists don't have an items() method. When you try to loop with for res_cat, resources in rescat2idx.items():, Python will throw an AttributeError: 'list' object has no attribute 'items'.

I suspect you meant to assign rescat2idx directly to the OrderedDict (drop the outer square brackets and the trailing 174).

Second error: Typo in variable name #

You created a dict called trans_time_max, but in the loop you wrote time_trans_max['TR_S%d' % ...]—missing an s in the variable name. This will cause a NameError: name 'time_trans_max' is not defined.

Fixed code and max_wait_time logic #

If we fix those two issues, here's the working code:

from collections import OrderedDict

rescat2idx = OrderedDict([
    ('EAF', [1]), ('AOD', [2]), ('LF', [3]), ('CC1', [4]), ('CC2', [5]),
    ('H_A_S1', range(6, 30)), ('H_A_S2', range(30, 54)), ('H_B_S2', range(54, 78)),
    ('H_A_S3', range(78, 102)), ('H_B_S3', range(102, 126)),
    ('H_A_S4', range(126, 150)), ('H_B_S4', range(150, 174)), ('EN', [174])
])
trans_time = {'TR_S1': 10, 'TR_S2': 4, 'TR_S3': 10}
trans_time_max = {'TR_S1': 240, 'TR_S2': 240, 'TR_S3': 120}

for res_cat, resources in rescat2idx.items():
    if 'H_B_' not in res_cat:
        continue
    max_wait_time = trans_time_max['TR_S%d' % (int(res_cat[-1]) - 1)]
    print(f"res_cat: {res_cat}, max_wait_time: {max_wait_time}")

Now let's clarify the max_wait_time logic you're confused about:

• res_cat is a string key from the OrderedDict—the ones that pass the 'H_B_' check are 'H_B_S2', 'H_B_S3', 'H_B_S4'
• res_cat[-1] grabs the last character of the string: for 'H_B_S2', that's '2'; for 'H_B_S3', it's '3'; for 'H_B_S4', it's '4'
• We convert that character to an integer, subtract 1: int('2') -1 =1, int('3')-1=2, int('4')-1=3
• That number gets plugged into 'TR_S%d' to make keys like 'TR_S1', 'TR_S2', 'TR_S3'
• Finally, we look up those keys in trans_time_max to get the max wait time

When you run the fixed code, the output will be:

res_cat: H_B_S2, max_wait_time: 240
res_cat: H_B_S3, max_wait_time: 240
res_cat: H_B_S4, max_wait_time: 120

内容的提问来源于stack exchange，提问作者Margi Shah