DataFrame 取值

通过 DataFrame[ ]方式，取得得都是行， [ ] 中，添加过滤条件

data = pd.DataFrame(

    np.arange(16).reshape(4,4),

    index=['OP','CW','UZ','NM'],

    columns=['one','two','three','four']

)

# print data

     # one  two  three  four

# OP    0    1      2     3

# CW    4    5      6     7

# UZ    8    9     10    11

# NM   12   13     14    15

# print data['one']

# <class 'pandas.core.series.Series'>

#  x.shape  (4,)

# OP     0

# CW     4

# UZ     8

# NM    12

# Name: one, dtype: int64

# print type(data[['one','two']])

# <class 'pandas.core.frame.DataFrame'>

# x.shape (4,2)

    # one  two

# OP    0    1

# CW    4    5

# UZ    8    9

# NM   12   13

# print data[:2]

# <class 'pandas.core.frame.DataFrame'>

# .shape (2,4)

    # one  two  three  four

# OP    0    1      2     3

# CW    4    5      6     7

# print data>5

      # one    two  three   four

# OP  False  False  False  False

# CW  False  False   True   True

# UZ   True   True   True   True

# NM   True   True   True   True

# print data[data['three']>5]

# x.shape (3,4)

#     one  two  three  four

# CW    4    5      6     7

# UZ    8    9     10    11

# NM   12   13     14    15

# print data[data>5]

#      one   two  three  four

# OP   NaN   NaN    NaN   NaN

# CW   NaN   NaN    6.0   7.0

# UZ   8.0   9.0   10.0  11.0

# NM  12.0  13.0   14.0  15.0

# data[data<5] = 0

# print data

    # one  two  three  four

# OP    0    0      0     0

# CW    0    5      6     7

# UZ    8    9     10    11

# NM   12   13     14    15

print data[2] # 报错。

print data.ix[2] #  √