python - 如何使用单个命令 [Python - Pandas] 获取所有列的数据类型？

Question

我想查看存储在我的数据框中的所有列的数据类型，而无需遍历它们。路在何方？

Answer 1

10 min to pandas有很好的例子 DataFrame.dtypes :

df2 = pd.DataFrame({ 
    'A' : 1.,
    'B' : pd.Timestamp('20130102'),
    'C' : pd.Series(1,index=list(range(4)),dtype='float32'),
    'D' : np.array([3] * 4,dtype='int32'),
    'E' : pd.Categorical(["test","train","test","train"]),
    'F' : 'foo' })

print (df2)
     A          B    C  D      E    F
0  1.0 2013-01-02  1.0  3   test  foo
1  1.0 2013-01-02  1.0  3  train  foo
2  1.0 2013-01-02  1.0  3   test  foo
3  1.0 2013-01-02  1.0  3  train  foo

print (df2.dtypes)
A           float64
B    datetime64[ns]
C           float32
D             int32
E          category
F            object
dtype: object

但是用dtypes=object就有点复杂了(一般来说，明明是string):

示例:

df = pd.DataFrame({'strings':['a','d','f'],
                   'dicts':[{'a':4}, {'c':8}, {'e':9}],
                   'lists':[[4,8],[7,8],[3]],
                   'tuples':[(4,8),(7,8),(3,)],
                   'sets':[set([1,8]), set([7,3]), set([0,1])] })

print (df)
      dicts   lists    sets strings  tuples
0  {'a': 4}  [4, 8]  {8, 1}       a  (4, 8)
1  {'c': 8}  [7, 8]  {3, 7}       d  (7, 8)
2  {'e': 9}     [3]  {0, 1}       f    (3,)

所有值都相同 dtypes :

print (df.dtypes)
dicts      object
lists      object
sets       object
strings    object
tuples     object
dtype: object

但是type是不同的，如果需要循环检查:

for col in df:
    print (df[col].apply(type))

0    <class 'dict'>
1    <class 'dict'>
2    <class 'dict'>
Name: dicts, dtype: object
0    <class 'list'>
1    <class 'list'>
2    <class 'list'>
Name: lists, dtype: object
0    <class 'set'>
1    <class 'set'>
2    <class 'set'>
Name: sets, dtype: object
0    <class 'str'>
1    <class 'str'>
2    <class 'str'>
Name: strings, dtype: object
0    <class 'tuple'>
1    <class 'tuple'>
2    <class 'tuple'>
Name: tuples, dtype: object

或列的第一个值 iat :

print (type(df['strings'].iat[0]))
<class 'str'>

print (type(df['dicts'].iat[0]))
<class 'dict'>

print (type(df['lists'].iat[0]))
<class 'list'>

print (type(df['tuples'].iat[0]))
<class 'tuple'>

print (type(df['sets'].iat[0]))
<class 'set'>