【笔记】初识Pandas

2019年01月01日 |

数据分析

| 数据分析 Pandas

Series 是个定长的字典序列

因为在存储数据的时候，相当于两个ndarray，这也是和字典最大的不同。因为在字典的结构里，元素的个数是不固定的。

Series有两个基本属性：index和values。默认index是0，1，2……递增的整数序列，也可以自己指定索引, index = [‘a’, ‘b’, ‘c’, ‘d’]

import pandas as pd
from pandas import Series, DataFrame

x1 = Series([1,2,3,4])
x2 = Series([1,2,3,4], ['a','b','c','d'])

# 采用字典的方式创建Series
d = {'a': 1, 'b':2, 'c':3, 'd':4}
x3 = Series(d)

print(x1)
print(x2)
print(x3)

执行结果：

0    1
1    2
2    3
3    4
dtype: int64
a    1
b    2
c    3
d    4
dtype: int64

DataFrame数据结构类型类似数据库表

import pandas as pd
from pandas import Series, DataFrame
data = {'Chinese': [66, 95, 93, 90,80],'English': [65, 85, 92, 88, 90],'Math': [30, 98, 96, 77, 90]}
df1= DataFrame(data)
df2 = DataFrame(data, index=['ZhangFei', 'GuanYu', 'ZhaoYun', 'HuangZhong', 'DianWei'], columns=['English', 'Math', 'Chinese'])
print(df1)
print(df2)

执行结果：

   Chinese  English  Math
0       66       65    30
1       95       85    98
2       93       92    96
3       90       88    77
4       80       90    90
            English  Math  Chinese
ZhangFei         65    30       66
GuanYu           85    98       95
ZhaoYun          92    96       93
HuangZhong       88    77       90
DianWei          90    90       80

数据导入和导出

import pandas as pd
from pandas import Series, DataFrame
data = {'Chinese': [66, 95, 93, 90,80],'English': [65, 85, 92, 88, 90],'Math': [30, 98, 96, 77, 90]}
score = DataFrame(data, index=['ZhangFei', 'GuanYu', 'ZhaoYun', 'HuangZhong', 'DianWei'], columns=['English', 'Math', 'Chinese'])
score.to_excel('data.xlsx')

# 导入excel表格
inputScores = DataFrame(pd.read_excel('data.xlsx'))
print(inputScores)

            English  Math  Chinese
ZhangFei         65    30       66
GuanYu           85    98       95
ZhaoYun          92    96       93
HuangZhong       88    77       90
DianWei          90    90       80

数据清洗

删除DataFrame的行或列

import pandas as pd
from pandas import Series, DataFrame
data = {'Chinese': [66, 95, 93, 90,80],'English': [65, 85, 92, 88, 90],'Math': [30, 98, 96, 77, 90]}
df2 = DataFrame(data, index=['ZhangFei', 'GuanYu', 'ZhaoYun', 'HuangZhong', 'DianWei'], columns=['English', 'Math', 'Chinese'])

# 删除列
df2 = df2.drop(columns=['Chinese'])
print(df2)

# 删除行
df2 = df2.drop(index=['ZhangFei'])
print(df2)

执行结果：

            English  Math
ZhangFei         65    30
GuanYu           85    98
ZhaoYun          92    96
HuangZhong       88    77
DianWei          90    90

            English  Math
GuanYu           85    98
ZhaoYun          92    96
HuangZhong       88    77
DianWei          90    90

重命名列名

# 紧接上面代码
# 对列名重命名
df2.rename(columns={'Math': 'Shuxue', 'English': 'Yingyu'}, inplace = True)
print(df2)

执行结果：

            Yingyu  Shuxue
GuanYu          85      98
ZhaoYun         92      96
HuangZhong      88      77
DianWei         90      90

去除重复的值

# 紧接上面代码
duplicateDf = DataFrame({'Shuxue': [90], 'Yingyu': [90]}, index=['Weiyan'])
df2 = df2.append(duplicateDf, sort=True)
print(df2)
df2 = df2.drop_duplicates() # 去除重复行
print(df2)

执行结果：

            Shuxue  Yingyu
GuanYu          98      85
ZhaoYun         96      92
HuangZhong      77      88
DianWei         90      90
Weiyan          90      90
            Shuxue  Yingyu
GuanYu          98      85
ZhaoYun         96      92
HuangZhong      77      88
DianWei         90      90

格式问题

更改数据格式