Pandas-27.文件读取

read_csv和readtable()可以将文件中的内容转换为DataFrame对象：

pandas.read_csv(filepath_or_buffer, sep=',', delimiter=None, header='infer',
names=None, index_col=None, usecols=None)

以如下csv文件为例：

S.No,Name,Age,City,Salary
1,Tom,28,Toronto,20000
2,Lee,32,HongKong,3000
3,Steven,43,Bay Area,8300
4,Ram,38,Hyderabad,3900

• 直接读取：

df=pd.read_csv("temp.csv")
print (df)

• index_col自定义索引：

df=pd.read_csv("temp.csv",index_col=['S.No'])
print (df)
'''
        Name  Age       City  Salary
S.No                                
1        Tom   28    Toronto   20000
2        Lee   32   HongKong    3000
3     Steven   43   Bay Area    8300
4        Ram   38  Hyderabad    3900
'''

• dtype指定类型：

df = pd.read_csv("temp.csv", dtype={'Salary': np.float64})
print (df.dtypes)
'''
S.No        int64
Name       object
Age         int64
City       object
Salary    float64
dtype: object
'''

• names指定标题名称,header指定首行

df=pd.read_csv("temp.csv", names=['a', 'b', 'c','d','e'])
print (df)
'''
      a       b    c          d       e
0  S.No    Name  Age       City  Salary
1     1     Tom   28    Toronto   20000
2     2     Lee   32   HongKong    3000
3     3  Steven   43   Bay Area    8300
4     4     Ram   38  Hyderabad    3900
'''
df=pd.read_csv("temp.csv", names=['a', 'b', 'c','d','e'],header=0)
print (df)
'''
      a       b    c          d       e
0     1     Tom   28    Toronto   20000
1     2     Lee   32   HongKong    3000
2     3  Steven   43   Bay Area    8300
3     4     Ram   38  Hyderabad    3900
'''

• skiprows跳过指定的行数

df=pd.read_csv("temp.csv", skiprows=2)
print (df)
'''
   2     Lee  32   HongKong  3000
0  3  Steven  43   Bay Area  8300
1  4     Ram  38  Hyderabad  3900
'''