解決 ValueError：無法將浮點 NaN 轉換為整數

Question

我正在編寫一個函數，該函數返回一個字典，其中數據集中所有引用的創建日期的年份用作鍵，作為值，它指定函數do_get_citations_per_year返回的兩個項目的元組。

def do_get_citations_per_year(data, year):
    result = tuple()
    my_ocan['creation'] = pd.DatetimeIndex(my_ocan['creation']).year

    len_citations = len(my_ocan.loc[my_ocan["creation"] == year, "creation"])
    timespan = my_ocan.loc[my_ocan["creation"] == year, "timespan"].fillna(0).mean()

    result = (len_citations, round(timespan))

    return result

def do_get_citations_all_years(data):
    mydict = {}
    s = set(my_ocan.creation)
    print(s)
    for year in s:
        mydict[year] = do_get_citations_per_year(data, year)
    #print(mydict)
    return mydict

我不斷收到錯誤消息：

(32, 240)
{2016, 2017, 2018, 2013, 2015}
  File "/Users/lisa/Desktop/yopy/execution_example.py", line 28, in <module>
    print(my_ocan.get_citations_all_years())
  File "/Users/lisa/Desktop/yopy/ocan.py", line 35, in get_citations_all_years
    return do_get_citations_all_years(self.data)
  File "/Users/lisa/Desktop/yopy/lisa.py", line 113, in do_get_citations_all_years
    mydict[year] = do_get_citations_per_year(data, year)
  File "/Users/lisa/Desktop/yopy/lisa.py", line 103, in do_get_citations_per_year
    result = (len_citations, round(timespan))
ValueError: cannot convert float NaN to integer

Process finished with exit code 1

更新：為了提供一個工作示例，我在這里發布了其他函數，特別是處理我的數據幀 (my_ocan) do_process_citation_data(f_path)和我的解析函數parse_timespan函數：

def do_process_citation_data(f_path):
    global my_ocan

    my_ocan = pd.read_csv(f_path, names=['oci', 'citing', 'cited', 'creation', 'timespan', 'journal_sc', 'author_sc'],
                          parse_dates=['creation', 'timespan'])
    my_ocan = my_ocan.iloc[1:]  # to remove the first row
    my_ocan['creation'] = pd.to_datetime(my_ocan['creation'], format="%Y-%m-%d", yearfirst=True)
    my_ocan['timespan'] = my_ocan['timespan'].map(parse_timespan)

    print(my_ocan['timespan'])

    return my_ocan

    #print(my_ocan['timespan'])

timespan_regex = re.compile(r'P(?:(\d+)Y)?(?:(\d+)M)?(?:(\d+)D)?')
def parse_timespan(timespan):
    # check if the input is a valid timespan
    if not timespan or 'P' not in timespan:
        return None

    # check if timespan is negative and skip initial 'P' literal
    curr_idx = 0
    is_negative = timespan.startswith('-')
    if is_negative:
        curr_idx = 1

    # extract years, months and days with the regex
    match = timespan_regex.match(timespan[curr_idx:])

    years = int(match.group(1) or 0)
    months = int(match.group(2) or 0)
    days = int(match.group(3) or 0)

    timespan_days = years * 365 + months * 30 + days

    return timespan_days if not is_negative else -timespan_days

當我打印 my_ocan['timespan']

我得到：

1        486.0
2       1080.0
3        730.0
4        824.0
5        365.0
6          0.0
...

我認為問題是 0.0

我怎樣才能解決這個浮點 NaN 到整數問題？

先感謝您！

Answer 1

我試過用python 2.7這個：

>>> round(float('NaN'))
nan
>>> round(float(0.0))
0.0

這與python 3.6：

>>> round(float('NaN'))
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: cannot convert float NaN to integer
>>> round(float(0.0))
0

因此，您似乎將任何 NaN 值放入輪函數中。 您可以使用 try except 語句來管理此問題：

try:
    result = (len_citations, round(timespan))
except ValueError:
    result = (len_citations, 0)