Python TypeError: cannot convert dictionary update sequence element #1 to a sequence

Question

doing some data wrangling from an example in O'Reilly's "Python for Data Analysis."

We start with data of the following format:

In [108]: data.CATEGORY[:5]
Out[108]: 
0          1. Urgences | Emergency, 3. Public Health, 
4                            1. Urgences | Emergency, 
5                       5e. Communication lines down, 
6    4. Menaces | Security Threats, 4e. Assainissem...
7                      4. Menaces | Security Threats, 
Name: CATEGORY, dtype: object

The book then lays out a procedure for removing the periods and '|' from each entry with the goal of creating a dictionary, using the following definitions;

def get_all_categories(cat_series):
    cat_sets = (set(to_cat_list(x)) for x in cat_series)
    return sorted(set.union(*cat_sets))

def get_english(cat):
    code, names = cat.split('.')
    if '|' in names:
        names = names.split(' | ')[1]
    return code, names.strip()

The first step goes fine, creating the list of unique categories;

In [109]: all_cats = get_all_categories(data.CATEGORY)

In [110]: all_cats[:5]
Out[110]: 
['1. Urgences | Emergency',
 '1a. Highly vulnerable',
 '1b. Urgence medicale | Medical Emergency',
 '1c. Personnes prises au piege | People trapped',
 '1d. Incendie | Fire']

However, using the second definition results in the following;

In [116]: english_mapping = dict(get_english(x) for x in all_cats)
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-116-e69c3419c341> in <module>()
----> 1 english_mapping = dict(get_english(x) for x in all_cats)

TypeError: cannot convert dictionary update sequence element #1 to a sequence

A little help for a Python noob please :)

I do not get this error when run on the input data you have provided. — Scott Hunter
– Scott Hunter, Commented Dec 20, 2014 at 0:09
Just tried it again on a different computer and I continue to get the same TypeError. I forgot to type in the following definition which is necessary for the get_all_categories definition: def to_cat_list(catstr): stripped = (x.strip() for x in catstr.split(',')) return [x for x in stripped if x] Not sure how you got the code to work without that Scott... — user3334415
– user3334415, Commented Dec 20, 2014 at 16:54
@user3334415 I also did not get an error. Link here: codepad.org/4uYUiIoS Caveat: I took a shortcut and simply used the excerpt you posted for all_cats (the first five elements) in a direct assignment, but I don't know enough about the full data you are loading to know whether that would cause your outcome to be different. — rchang
– rchang, Commented Dec 21, 2014 at 2:51

bob.song · Accepted Answer · 2015-12-15 15:04:28Z

3

Here is the solution:

"cannot convert dictionary update sequence element #1 to a sequence"---because there is null value in the expression "get_english(x) for x in all_cats", so it can't be converted into a dictionary;
Why?

def get_english(cat):
    code,names=cat.split('.')
    if '|' in names:
        names=names.split('|')[1]
        return code,names.strip()

----Here is the problem,the last line shouldn't indent，if not,you will get some value null.

edited Dec 15, 2015 at 15:04

answered Dec 15, 2015 at 14:54

bob.song

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