pandas浅析

创建DataFrame

import pandas as pd

1. 读取csv文件并转为DataFrame

   csv_data = pd.read_csv("test_data.csv", encoding = "ISO-8859-1")

2. 字典转为DataFrame

   d = {'col1': [1, 2], 'col2': [3, 4]}
   df = pd.DataFrame(data=d)

   	col1	col2
   0	1	3
   1	2	4

3. 双层列表转为DataFrame

   data = [['tom', 10], ['nick', 15], ['juli', 14]] 
   
   # Create the pandas DataFrame 
   df = pd.DataFrame(data, columns = ['Name', 'Age']) 

   	Name	Age
   0	tom	10
   1	nick	15
   2	juli	14

4. 列表字典转DataFrame

   data = [{'a': 1, 'b': 2, 'c':3}, 
           {'a':10, 'b': 20, 'c': 30}] 
   
   # Creates DataFrame. 
   df = pd.DataFrame(data) 

   	a	b	c
   0	1	2	3
   1	10	20	30

5. 指定index

   df = pd.DataFrame(data, index =['rank1', 
                                   'rank2', 
                                   'rank3', 
                                   'rank4'])

修改DataFrame值

1. 修改一列的值

   df["data"] = df["data"].map(lambda x: 0)

2. 修改多列的值

   for index, row in df_res.iterrows():
       df_res.at[index, 'data1'] = 0
       df_res.at[index, 'data2'] = 0

类型转换

1. 整体转为str

   df = df.astype(str)

2. 整体转为int

   df = df.astype(int)