为了检查值是否为 NaN,可以使用 isnull() 或notnull() 函数。 In [1]: import numpy as np In [2]: import pandas as pd In [3]: ser = pd.Series([1, 2, np.nan, 4]) In [4]: pd.isnull(ser) Out[4]: 0 False 1 False 2 True 3 False dtype: bool 请注意,np.nan == np.nan...
We can add an extension to create an empty list public static IEnumerable<T> Nullable<T>(this IEnumerable<T> obj) { if (obj == null) return new List<T>(); else return obj; } And use like this foreach (model in models.Nullable()) { ... }...
To utilize df as a name in your if statement, it is necessary to assign it a value. Suitable empty values includeNoneand a dataframe without any rows. Let's assume the latter option. import pandas df = None for i in range(100): if df is None: # Your default dataframe here. # You...