python Pandas之DataFrame索引及选取数据

myList = [['a', 10, 1.1],
	  ['b', 20, 2.2],
	  ['c', 30, 3.3],
	  ['d', 40, 4.4]]
df1 = pd.DataFrame(data = myList)
print(df1)
--------------------------------
[out]:
   0   1    2
0  a  10  1.1
1  b  20  2.2
2  c  30  3.3
3  d  40  4.4

# 输出行索引
print(df1.index)
[out]:
RangeIndex(start=0, stop=4, step=1)
---------------------------------------
# 输出列索引
print(df1.columns)
[out]:
RangeIndex(start=0, stop=3, step=1)
---------------------------------------
# 输出所有的值
print(df1.values)
[out]:
array([['a', 10, 1.1],
       ['b', 20, 2.2],
       ['c', 30, 3.3],
       ['d', 40, 4.4]], dtype=object)

df2 = pd.DataFrame(myList, 
		           index = ['one', 'two', 'three', 'four'], 
		           columns = ['char', 'int', 'float'])
print(df2)
-----------------------------------------------------------
[out]:
      char  int  float
one      a   10    1.1
two      b   20    2.2
three    c   30    3.3
four     d   40    4.4

print(df2['char'])
print(df2.char)
# 两种方式输出一样
[out]:
one      a
two      b
three    c
four     d
Name: char, dtype: object

print(df2['char'])
print(df2.char)
# 两种方式输出一样
[out]:
one      a
two      b
three    c
four     d
Name: char, dtype: object

print(df2[['char', 'int']])
[out]: 
      char   int
one      a   10
two      b   20
three    c   30
four     d   40

print(df2[['char']])
[out]:
      char
one      a
two      b
three    c
four     d
---------------------------------------
type(df2[['char']])
[out]：pandas.core.frame.DataFrame

print(df1[0])
[out]:
0    a
1    b
2    c
3    d
Name: 0, dtype: object
-----------------------
print(df2[0])
[out]: 
KeyError: 0

print(df2['two': 'three'])
[out]:
      char  int  float
two      b   20    2.2
three    c   30    3.3

# 此时返回的类型为DataFrame
print(df2['two': 'two'])
[out]:
      char  int  float
two      b   20    2.2

print(df2[1:4])
[out]:
      char  int  float
two      b   20    2.2
three    c   30    3.3
four     d   40    4.4

print(df2[1:2])
[out]:
    char  int  float
two    b   20    2.2

print(df2.loc['one'])
[out]:
char       a
int       10
float    1.1
Name: one, dtype: object
-------------------------------------------
print(df2.loc[['one', 'three']])
[out]:
      char  int  float
one      a   10    1.1
three    c   30    3.3

print(df2.iloc[0])
[out]:
char       a
int       10
float    1.1
Name: one, dtype: object
-------------------------------------------
print(df2.iloc[[0, 2]])
[out]:
      char  int  float
one      a   10    1.1
three    c   30    3.3