100 个 pandas 案例,强烈建议收藏!

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  • 如何使用列表和字典创建 Series
  • 使用列表创建 Series
  • 使用 name 参数创建 Series
  • 使用简写的列表创建 Series
  • 使用字典创建 Series
  • 如何使用 Numpy 函数创建 Series
  • 如何获取 Series 的索引和值
  • 如何在创建 Series 时指定索引
  • 如何获取 Series 的大小和形状
  • 如何获取 Series 开始或末尾几行数据
  • Head()
  • Tail()
  • Take()
  • 使用切片获取 Series 子集
  • 如何创建 DataFrame
  • 如何设置 DataFrame 的索引和列信息
  • 如何重命名 DataFrame 的列名称
  • 如何根据 Pandas 列中的值从 DataFrame 中选择或过滤行
  • 在 DataFrame 中使用“isin”过滤多行
  • 迭代 DataFrame 的行和列
  • 如何通过名称或索引删除 DataFrame 的列
  • 向 DataFrame 中新增列
  • 如何从 DataFrame 中获取列标题列表
  • 如何随机生成 DataFrame
  • 如何选择 DataFrame 的多个列
  • 如何将字典转换为 DataFrame
  • 使用 ioc 进行切片
  • 检查 DataFrame 中是否是空的
  • 在创建 DataFrame 时指定索引和列名称
  • 使用 iloc 进行切片
  • iloc 和 loc 的区别
  • 使用时间索引创建空 DataFrame
  • 如何改变 DataFrame 列的排序
  • 检查 DataFrame 列的数据类型
  • 更改 DataFrame 指定列的数据类型
  • 如何将列的数据类型转换为 DateTime 类型
  • 将 DataFrame 列从 floats 转为 ints
  • 如何把 dates 列转换为 DateTime 类型
  • 两个 DataFrame 相加
  • 在 DataFrame 末尾添加额外的行
  • 为指定索引添加新行
  • 如何使用 for 循环添加行
  • 在 DataFrame 顶部添加一行
  • 如何向 DataFrame 中动态添加行
  • 在任意位置插入行
  • 使用时间戳索引向 DataFrame 中添加行
  • 为不同的行填充缺失值
  • append, concat 和 combine_first 示例
  • 获取行和列的平均值
  • 计算行和列的总和
  • 连接两列
  • 过滤包含某字符串的行
  • 过滤索引中包含某字符串的行
  • 使用 AND 运算符过滤包含特定字符串值的行
  • 查找包含某字符串的所有行
  • 如果行中的值包含字符串,则创建与字符串相等的另一列
  • 计算 pandas group 中每组的行数
  • 检查字符串是否在 DataFrme 中
  • 从 DataFrame 列中获取唯一行值
  • 计算 DataFrame 列的不同值
  • 删除具有重复索引的行
  • 删除某些列具有重复值的行
  • 从 DataFrame 单元格中获取值
  • 使用 DataFrame 中的条件索引获取单元格上的标量值
  • 设置 DataFrame 的特定单元格值
  • 从 DataFrame 行获取单元格值
  • 用字典替换 DataFrame 列中的值
  • 统计基于某一列的一列的数值
  • 处理 DataFrame 中的缺失值
  • 删除包含任何缺失数据的行
  • 删除 DataFrame 中缺失数据的列
  • 按降序对索引值进行排序
  • 按降序对列进行排序
  • 使用 rank 方法查找 DataFrame 中元素的排名
  • 在多列上设置索引
  • 确定 DataFrame 的周期索引和列
  • 导入 CSV 指定特定索引
  • 将 DataFrame 写入 csv
  • 使用 Pandas 读取 csv 文件的特定列
  • Pandas 获取 CSV 列的列表
  • 找到列值最大的行
  • 使用查询方法进行复杂条件选择
  • 检查 Pandas 中是否存在列
  • 为特定列从 DataFrame 中查找 n-smallest 和 n-largest 值
  • 从 DataFrame 中查找所有列的最小值和最大值
  • 在 DataFrame 中找到最小值和最大值所在的索引位置
  • 计算 DataFrame Columns 的累积乘积和累积总和
  • 汇总统计
  • 查找 DataFrame 的均值、中值和众数
  • 测量 DataFrame 列的方差和标准偏差
  • 计算 DataFrame 列之间的协方差
  • 计算 Pandas 中两个 DataFrame 对象之间的相关性
  • 计算 DataFrame 列的每个单元格的百分比变化
  • 在 Pandas 中向前和向后填充 DataFrame 列的缺失值
  • 在 Pandas 中使用非分层索引使用 Stacking
  • 使用分层索引对 Pandas 进行拆分
  • Pandas 获取 html 页面上 table 数据

1如何使用列表和字典创建 Series

使用列表创建 Series

import pandas as pd

ser1 = pd.Series([1.5, 2.5, 3, 4.5, 5.0, 6])
print(ser1)

Output:

0    1.5
1 2.5
2 3.0
3 4.5
4 5.0
5 6.0
dtype: float64

使用 name 参数创建 Series

import pandas as pd

ser2 = pd.Series(["India", "Canada", "Germany"], name="Countries")
print(ser2)

Output:

0      India
1 Canada
2 Germany
Name: Countries, dtype: object

使用简写的列表创建 Series

import pandas as pd

ser3 = pd.Series(["A"]*4)
print(ser3)

Output:

0    A
1 A
2 A
3 A
dtype: object

使用字典创建 Series

import pandas as pd

ser4 = pd.Series("India": "New Delhi",
"Japan": "Tokyo",
"UK": "London")
print(ser4)

Output:

India    New Delhi
Japan Tokyo
UK London
dtype: object

2如何使用 Numpy 函数创建 Series

import pandas as pd
import numpy as np

ser1 = pd.Series(np.linspace(1, 10, 5))
print(ser1)

ser2 = pd.Series(np.random.normal(size=5))
print(ser2)

Output:

0     1.00
1 3.25
2 5.50
3 7.75
4 10.00
dtype: float64
0 -1.694452
1 -1.570006
2 1.713794
3 0.338292
4 0.803511
dtype: float64

3如何获取 Series 的索引和值

import pandas as pd
import numpy as np

ser1 = pd.Series("India": "New Delhi",
"Japan": "Tokyo",
"UK": "London")

print(ser1.values)
print(ser1.index)

print("\\n")

ser2 = pd.Series(np.random.normal(size=5))
print(ser2.index)
print(ser2.values)

Output:

[New Delhi Tokyo London]
Index([India, Japan, UK], dtype=object)


RangeIndex(start=0, stop=5, step=1)
[ 0.66265478 -0.72222211 0.3608642 1.40955436 1.3096732 ]

4如何在创建 Series 时指定索引

import pandas as pd

values = ["India", "Canada", "Australia",
"Japan", "Germany", "France"]

code = ["IND", "CAN", "AUS", "JAP", "GER", "FRA"]

ser1 = pd.Series(values, index=code)

print(ser1)

Output:

IND        India
CAN Canada
AUS Australia
JAP Japan
GER Germany
FRA France
dtype: object

5如何获取 Series 的大小和形状

import pandas as pd

values = ["India", "Canada", "Australia",
"Japan", "Germany", "France"]

code = ["IND", "CAN", "AUS", "JAP", "GER", "FRA"]

ser1 = pd.Series(values, index=code)

print(len(ser1))

print(ser1.shape)

print(ser1.size)

Output:

6
(6,)
6

6如何获取 Series 开始或末尾几行数据

Head()

import pandas as pd

values = ["India", "Canada", "Australia",
"Japan", "Germany", "France"]

code = ["IND", "CAN", "AUS", "JAP", "GER", "FRA"]

ser1 = pd.Series(values, index=code)

print("-----Head()-----")
print(ser1.head())

print("\\n\\n-----Head(2)-----")
print(ser1.head(2))

Output:

-----Head()-----
IND India
CAN Canada
AUS Australia
JAP Japan
GER Germany
dtype: object


-----Head(2)-----
IND India
CAN Canada
dtype: object

Tail()

import pandas as pd

values = ["India", "Canada", "Australia",
"Japan", "Germany", "France"]

code = ["IND", "CAN", "AUS", "JAP", "GER", "FRA"]

ser1 = pd.Series(values, index=code)

print("-----Tail()-----")
print(ser1.tail())

print("\\n\\n-----Tail(2)-----")
print(ser1.tail(2))

Output:

-----Tail()-----
CAN Canada
AUS Australia
JAP Japan
GER Germany
FRA France
dtype: object


-----Tail(2)-----
GER Germany
FRA France
dtype: object

Take()

import pandas as pd

values = ["India", "Canada", "Australia",
"Japan", "Germany", "France"]

code = ["IND", "CAN", "AUS", "JAP", "GER", "FRA"]

ser1 = pd.Series(values, index=code)

print("-----Take()-----")
print(ser1.take([2, 4, 5]))

Output:

-----Take()-----
AUS Australia
GER Germany
FRA France
dtype: object

7使用切片获取 Series 子集

import pandas as pd

num = [000, 100, 200, 300, 400, 500, 600, 700, 800, 900]

idx = [A, B, C, D, E, F, G, H, I, J]

series = pd.Series(num, index=idx)

print("\\n [2:2] \\n")
print(series[2:4])

print("\\n [1:6:2] \\n")
print(series[1:6:2])

print("\\n [:6] \\n")
print(series[:6])

print("\\n [4:] \\n")
print(series[4:])

print("\\n [:4:2] \\n")
print(series[:4:2])

print("\\n [4::2] \\n")
print(series[4::2])

print("\\n [::-1] \\n")
print(series[::-1])

Output

[2:2]

C 200
D 300
dtype: int64

[1:6:2]

B 100
D 300
F 500
dtype: int64

[:6]

A 0
B 100
C 200
D 300
E 400
F 500
dtype: int64

[4:]

E 400
F 500
G 600
H 700
I 800
J 900
dtype: int64

[:4:2]

A 0
C 200
dtype: int64

[4::2]

E 400
G 600
I 800
dtype: int64

[::-1]

J 900
I 800
H 700
G 600
F 500
E 400
D 300
C 200
B 100
A 0
dtype: int64

8如何创建 DataFrame

import pandas as pd

employees = pd.DataFrame(
EmpCode: [Emp001, Emp00],
Name: [John Doe, William Spark],
Occupation: [Chemist, Statistician],
Date Of Join: [2018-01-25, 2018-01-26],
Age: [23, 24])

print(employees)

Output:

Age Date Of Join EmpCode           Name    Occupation
0 23 2018-01-25 Emp001 John Doe Chemist
1 24 2018-01-26 Emp00 William Spark Statistician

9如何设置 DataFrame 的索引和列信息

import pandas as pd

employees = pd.DataFrame(
data=Name: [John Doe, William Spark],
Occupation: [Chemist, Statistician],
Date Of Join: [2018-01-25, 2018-01-26],
Age: [23, 24],
index=[Emp001, Emp002],
columns=[Name, Occupation, Date Of Join, Age])

print(employees)

Output

Name    Occupation Date Of Join  Age
Emp001 John Doe Chemist 2018-01-25 23
Emp002 William Spark Statistician 2018-01-26 24

10如何重命名 DataFrame 的列名称

import pandas as pd

employees = pd.DataFrame(
EmpCode: [Emp001, Emp00],
Name: [John Doe, William Spark],
Occupation: [Chemist, Statistician],
Date Of Join: [2018-01-25, 2018-01-26],
Age: [23, 24])

employees.columns = [EmpCode, EmpName, EmpOccupation, EmpDOJ, EmpAge]

print(employees)

Output:

EmpCode     EmpName EmpOccupation         EmpDOJ        EmpAge
0 23 2018-01-25 Emp001 John Doe Chemist
1 24 2018-01-26 Emp00 William Spark Statistician

11如何根据 Pandas 列中的值从 DataFrame 中选择或过滤行

import pandas as pd

employees = pd.DataFrame(
EmpCode: [Emp001, Emp002, Emp003, Emp004, Emp005],
Name: [John, Doe, William, Spark, Mark],
Occupation: [Chemist, Statistician, Statistician,
Statistician, Programmer],
Date Of Join: [2018-01-25, 2018-01-26, 2018-01-26, 2018-02-26,
2018-03-16],
Age: [23, 24, 34, 29, 40])

print("\\nUse == operator\\n")
print(employees.loc[employees[Age] == 23])

print("\\nUse < operator\\n")
print(employees.loc[employees[Age] < 30])

print("\\nUse != operator\\n")
print(employees.loc[employees[Occupation] != Statistician])

print("\\nMultiple Conditions\\n")
print(employees.loc[(employees[Occupation] != Statistician) &
(employees[Name] == John)])

Output:

Use == operator

Age Date Of Join EmpCode Name Occupation
0 23 2018-01-25 Emp001 John Chemist

Use < operator

Age Date Of Join EmpCode Name Occupation
0 23 2018-01-25 Emp001 John Chemist
1 24 2018-01-26 Emp002 Doe Statistician
3 29 2018-02-26 Emp004 Spark Statistician

Use != operator

Age Date Of Join EmpCode Name Occupation
0 23 2018-01-25 Emp001 John Chemist
4 40 2018-03-16 Emp005 Mark Programmer

Multiple Conditions

Age Date Of Join EmpCode Name Occupation
0 23 2018-01-25 Emp001 John Chemist

12在 DataFrame 中使用“isin”过滤多行

import pandas as pd

employees = pd.DataFrame(
EmpCode: [Emp001, Emp002, Emp003, Emp004, Emp005],
Name: [John, Doe, William, Spark, Mark],
Occupation: [Chemist, Statistician, Statistician,
Statistician, Programmer],
Date Of Join: [2018-01-25, 2018-01-26, 2018-01-26, 2018-02-26,
2018-03-16],
Age: [23, 24, 34, 29, 40])

print("\\nUse isin operator\\n")
print(employees.loc[employees[Occupation].isin([Chemist,Programmer])])

print("\\nMultiple Conditions\\n")
print(employees.loc[(employees[Occupation] == Chemist) |
(employees[Name] == John) &
(employees[Age] < 30)])

Output:

Use isin operator

Age Date Of Join EmpCode Name Occupation
0 23 2018-01-25 Emp001 John Chemist
4 40 2018-03-16 Emp005 Mark Programmer

Multiple Conditions

Age Date Of Join EmpCode Name Occupation
0 23 2018-01-25 Emp001 John Chemist

13迭代 DataFrame 的行和列

import pandas as pd

employees = pd.DataFrame(
EmpCode: [Emp001, Emp002, Emp003, Emp004, Emp005],
Name: [John, Doe, William, Spark, Mark],
Occupation: [Chemist, Statistician, Statistician,
Statistician, Programmer],
Date Of Join: [2018-01-25, 2018-01-26, 2018-01-26, 2018-02-26,
2018-03-16],
Age: [23, 24, 34, 29, 40])

print("\\n Example iterrows \\n")
for index, col in employees.iterrows():
print(col[Name], "--", col[Age])


print("\\n Example itertuples \\n")
for row in employees.itertuples(index=True, name=Pandas):
print(getattr(row, "Name"), "--", getattr(row, "Age"))

Output:

Example iterrows

John -- 23
Doe -- 24
William -- 34
Spark -- 29
Mark -- 40

Example itertuples

John -- 23
Doe -- 24
William -- 34
Spark -- 29
Mark -- 40

14如何通过名称或索引删除 DataFrame 的列

import pandas as pd

employees = pd.DataFrame(
EmpCode: [Emp001, Emp002, Emp003, Emp004, Emp005],
Name: [John, Doe, William, Spark, Mark],
Occupation: [Chemist, Statistician, Statistician,
Statistician, Programmer],
Date Of Join: [2018-01-25, 2018-01-26, 2018-01-26, 2018-02-26,
2018-03-16],
Age: [23, 24, 34, 29, 40])

print(employees)

print("\\n Drop Column by Name \\n")
employees.drop(Age, axis=1, inplace=True)
print(employees)

print("\\n Drop Column by Index \\n")
employees.drop(employees.columns[[0,1]], axis=1, inplace=True)
print(employees)

Output:

Age Date Of Join EmpCode     Name    Occupation
0 23 2018-01-25 Emp001 John Chemist
1 24 2018-01-26 Emp002 Doe Statistician
2 34 2018-01-26 Emp003 William Statistician
3 29 2018-02-26 Emp004 Spark Statistician
4 40 2018-03-16 Emp005 Mark Programmer

Drop Column by Name

Date Of Join EmpCode Name Occupation
0 2018-01-25 Emp001 John Chemist
1 2018-01-26 Emp002 Doe Statistician
2 2018-01-26 Emp003 William Statistician
3 2018-02-26 Emp004 Spark Statistician
4 2018-03-16 Emp005 Mark Programmer

Drop Column by Index

Name Occupation
0 John Chemist
1 Doe Statistician
2 William Statistician
3 Spark Statistician
4 Mark Programmer

15向 DataFrame 中新增列

import pandas as pd

employees = pd.DataFrame(
EmpCode: [Emp001, Emp002, Emp003, Emp004, Emp005],
Name: [John, Doe, William, Spark, Mark],
Occupation: [Chemist, Statistician, Statistician,
Statistician, Programmer],
Date Of Join: [2018-01-25, 2018-01-26, 2018-01-26, 2018-02-26,
2018-03-16],
Age: [23, 24, 34, 29, 40])

employees[City] = [London, Tokyo, Sydney, London, Toronto]

print(employees)

Output:

Age Date Of Join EmpCode     Name    Occupation     City
0 23 2018-01-25 Emp001 John Chemist London
1 24 2018-01-26 Emp002 Doe Statistician Tokyo
2 34 2018-01-26 Emp003 William Statistician Sydney
3 29 2018-02-26 Emp004 Spark Statistician London
4 40 2018-03-16 Emp005 Mark Programmer Toronto

16如何从 DataFrame 中获取列标题列表

import pandas as pd

employees = pd.DataFrame(
EmpCode: [Emp001, Emp002, Emp003, Emp004, Emp005],
Name: [John, Doe, William, Spark, Mark],
Occupation: [Chemist, Statistician, Statistician,
Statistician, Programmer],
Date Of Join: [2018-01-25, 2018-01-26, 2018-01-26, 2018-02-26,
2018-03-16],
Age: [23, 24, 34, 29, 40])

print(list(employees))

print(list(employees.columns.values))

print(employees.columns.tolist())

Output:

[Age, Date Of Join, EmpCode, Name, Occupation]
[Age, Date Of Join, EmpCode, Name, Occupation]
[Age, Date Of Join, EmpCode, Name, Occupation]

17如何随机生成 DataFrame

import pandas as pd
import numpy as np

np.random.seed(5)

df_random = pd.DataFrame(np.random.randint(100, size=(10, 6)),
columns=list(ABCDEF),
index=[Row-.format(i) for i in range(10)])

print(df_random)

Output:

A   B   C   D   E   F
Row-0 99 78 61 16 73 8
Row-1 62 27 30 80 7 76
Row-2 15 53 80 27 44 77
Row-3 75 65 47 30 84 86
Row-4 18 9 41 62 1 82
Row-5 16 78 5 58 0 80
Row-6 4 36 51 27 31 2
Row-7 68 38 83 19 18 7
Row-8 30 62 11 67 65 55
Row-9 3 91 78 27 29 33

18如何选择 DataFrame 的多个列

import pandas as pd

employees = pd.DataFrame(
EmpCode: [Emp001, Emp002, Emp003, Emp004, Emp005],
Name: [John, Doe, William, Spark, Mark],
Occupation: [Chemist, Statistician, Statistician,
Statistician, Programmer],
Date Of Join: [2018-01-25, 2018-01-26, 2018-01-26, 2018-02-26,
2018-03-16],
Age: [23, 24, 34, 29, 40])

df = employees[[EmpCode, Age, Name]]
print(df)

Output:

EmpCode  Age     Name
0 Emp001 23 John
1 Emp002 24 Doe
2 Emp003 34 William
3 Emp004 29 Spark
4 Emp005 40 Mark

19如何将字典转换为 DataFrame

import pandas as pd

data = (Age: [30, 20, 22, 40, 32, 28, 39],
Color: [Blue, Green, Red, White, Gray, Black,
Red],
Food: [Steak, Lamb, Mango, Apple, Cheese,
Melon, Beans],
Height: [165, 70, 120, 80, 180, 172, 150],
Score: [4.6, 8.3, 9.0, 3.3, 1.8, 9.5, 2.2],
State: [NY, TX, FL, AL, AK, TX, TX]
)
print(data)

df = pd.DataFrame(data)

print(df)

Output:

Height: [165, 70, 120, 80, 180, 172, 150], Food: [Steak, Lamb, Mango,
Apple, Cheese, Melon, Beans], Age: [30, 20, 22, 40, 32, 28, 39], Sco
re: [4.6, 8.3, 9.0, 3.3, 1.8, 9.5, 2.2], Color: [Blue, Green, Red, Whi
te, Gray, Black, Red], State: [NY, TX, FL, AL, AK, TX, TX
]
Age Color Food Height Score State
0 30 Blue Steak 165 4.6 NY
1 20 Green Lamb 70 8.3 TX
2 22 Red Mango 120 9.0 FL
3 40 White Apple 80 3.3 AL
4 32 Gray Cheese 180 1.8 AK
5 28 Black Melon 172 9.5 TX
6 39 Red Beans 150 2.2 TX

20使用 ioc 进行切片

import pandas as pd

df = pd.DataFrame(Age: [30, 20, 22, 40, 32, 28, 39],
Color: [Blue, Green, Red, White, Gray, Black,
Red],
Food: [Steak, Lamb, Mango, Apple, Cheese,
Melon, Beans],
Height: [165, 70, 120, 80, 180, 172, 150],
Score: [4.6, 8.3, 9.0, 3.3, 1.8, 9.5, 2.2],
State: [NY, TX, FL, AL, AK, TX, TX]
,
index=[Jane, Nick, Aaron, Penelope, Dean,
Christina, Cornelia])

print("\\n -- Selecting a single row with .loc with a string -- \\n")
print(df.loc[Penelope])

print("\\n -- Selecting multiple rows with .loc with a list of strings -- \\n")
print(df.loc[[Cornelia, Jane, Dean]])

print("\\n -- Selecting multiple rows with .loc with slice notation -- \\n")
print(df.loc[Aaron:Dean])

Output:

-- Selecting a single row with .loc with a string --

Age 40
Color White
Food Apple
Height 80
Score 3.3
State AL
Name: Penelope, dtype: object

-- Selecting multiple rows with .loc with a list of strings --

Age Color Food Height Score State
Cornelia 39 Red Beans 150 2.2 TX
Jane 30 Blue Steak 165 4.6 NY
Dean 32 Gray Cheese 180 1.8 AK

-- Selecting multiple rows with .loc with slice notation --

Age Color Food Height Score State
Aaron 22 Red Mango 120 9.0 FL
Penelope 40 White Apple 80 3.3 AL
Dean 32 Gray Cheese 180 1.8 AK

21检查 DataFrame 中是否是空的

import pandas as pd

df = pd.DataFrame()

if df.empty:
print(DataFrame is empty!)

Output:

DataFrame is empty!

22在创建 DataFrame 时指定索引和列名称

import pandas as pd

values = ["India", "Canada", "Australia",
"Japan", "Germany", "France"]

code = ["IND", "CAN", "AUS", "JAP", "GER", "FRA"]

df = pd.DataFrame(values, index=code, columns=[Country])

print(df)

Output:

Country
IND India
CAN Canada
AUS Australia
JAP Japan
GER Germany
FRA France

23使用 iloc 进行切片

import pandas as pd

df = pd.DataFrame(Age: [30, 20, 22, 40, 32, 28, 39],
Color: [Blue, Green, Red, White, Gray, Black,
Red],
Food: [Steak, Lamb, Mango, Apple, Cheese,
Melon, Beans],
Height: [165, 70, 120, 80, 180, 172, 150],
Score: [4.6, 8.3, 9.0, 3.3, 1.8, 9.5, 2.2],
State: [NY, TX, FL, AL, AK, TX, TX]
,
index=[Jane, Nick, Aaron, Penelope, Dean,
Christina, Cornelia])

print("\\n -- Selecting a single row with .iloc with an integer -- \\n")
print(df.iloc[4])

print("\\n -- Selecting multiple rows with .iloc with a list of integers -- \\n")
print(df.iloc[[2, -2]])

print("\\n -- Selecting multiple rows with .iloc with slice notation -- \\n")
print(df.iloc[:5:3])

Output:

-- Selecting a single row with .iloc with an integer --

Age 32
Color Gray
Food Cheese
Height 180
Score 1.8
State AK
Name: Dean, dtype: object

-- Selecting multiple rows with .iloc with a list of integers --

Age Color Food Height Score State
Aaron 22 Red Mango 120 9.0 FL
Christina 28 Black Melon 172 9.5 TX

-- Selecting multiple rows with .iloc with slice notation --

Age Color Food Height Score State
Jane 30 Blue Steak 165 4.6 NY
Penelope 40 White Apple 80 3.3 AL

24iloc 和 loc 的区别

  • loc 索引器还可以进行布尔选择,例如,如果我们想查找 Age 小于 30 的所有行并仅返回 Color 和 Height 列,我们可以执行以下操作。我们可以用 iloc 复制它,但我们不能将它传递给一个布尔系列,必须将布尔系列转换为 numpy 数组
  • loc 从索引中获取具有特定标签的行(或列)
  • iloc 在索引中的特定位置获取行(或列)(因此它只需要整数)
import pandas as pd

df = pd.DataFrame(Age: [30, 20, 22, 40, 32, 28, 39],
Color: [Blue, Green, Red, White, Gray, Black,
Red],
Food: [Steak, Lamb, Mango, Apple, Cheese,
Melon, Beans],
Height: [165, 70, 120, 80, 180, 172, 150],
Score: [4.6, 8.3, 9.0, 3.3, 1.8, 9.5, 2.2],
State: [NY, TX, FL, AL, AK, TX, TX]
,
index=[Jane, Nick, Aaron, Penelope, Dean,
Christina, Cornelia])

print("\\n -- loc -- \\n")
print(df.loc[df[Age] < 30, [Color, Height]])

print("\\n -- iloc -- \\n")
print(df.iloc[(df[Age] < 30).values, [1, 3]])

Output:

-- loc --

Color Height
Nick Green 70
Aaron Red 120
Christina Black 172

-- iloc --

Color Height
Nick Green 70
Aaron Red 120
Christina Black 172

25使用时间索引创建空 DataFrame

import datetime
import pandas as pd

todays_date = datetime.datetime.now().date()
index = pd.date_range(todays_date, periods=10, freq=D)

columns = [A, B, C]

df = pd.DataFrame(index=index, columns=columns)
df = df.fillna(0)

print(df)

Output:

A  B  C
2018-09-30 0 0 0
2018-10-01 0 0 0
2018-10-02 0 0 0
2018-10-03 0 0 0
2018-10-04 0 0 0
2018-10-05 0 0 0
2018-10-06 0 0 0
2018-10-07 0 0 0
2018-10-08 0 0 0
2018-10-09 0 0 0

26如何改变 DataFrame 列的排序

import pandas as pd

df = pd.DataFrame(Age: [30, 20, 22, 40, 32, 28, 39],
Color: [Blue, Green, Red, White, Gray, Black,
Red],
Food: [Steak, Lamb, Mango, Apple, Cheese,
Melon, Beans],
Height: [165, 70, 120, 80, 180, 172, 150],
Score: [4.6, 8.3, 9.0, 3.3, 1.8, 9.5, 2.2],
State: [NY, TX, FL, AL, AK, TX, TX]
,
index=[Jane, Nick, Aaron, Penelope, Dean,
Christina, Cornelia])

print("\\n -- Change order using columns -- \\n")
new_order = [3, 2, 1, 4, 5, 0]
df = df[df.columns[new_order]]
print(df)

print("\\n -- Change order using reindex -- \\n")
df = df.reindex([State, Color, Age, Food, Score, Height], axis=1)
print(df)

Output:

-- Change order using columns --

Height Food Color Score State Age
Jane 165 Steak Blue 4.6 NY 30
Nick 70 Lamb Green 8.3 TX 20
Aaron 120 Mango Red 9.0 FL 22
Penelope 80 Apple White 3.3 AL 40
Dean 180 Cheese Gray 1.8 AK 32
Christina 172 Melon Black 9.5 TX 28
Cornelia 150 Beans Red 2.2 TX 39

-- Change order using reindex --

State Color Age Food Score Height
Jane NY Blue 30 Steak 4.6 165
Nick TX Green 20 Lamb 8.3 70
Aaron FL Red 22 Mango 9.0 120
Penelope AL White 40 Apple 3.3 80
Dean AK Gray 32 Cheese 1.8 180
Christina TX Black 28 Melon 9.5 172
Cornelia TX Red 39 Beans 2.2 150

27检查 DataFrame 列的数据类型

import pandas as pd

df = pd.DataFrame(Age: [30, 20, 22, 40, 32, 28, 39],
Color: [Blue, Green, Red, White, Gray, Black,
Red],
Food: [Steak, Lamb, Mango, Apple, Cheese,
Melon, Beans],
Height: [165, 70, 120, 80, 180, 172, 150],
Score: [4.6, 8.3, 9.0, 3.3, 1.8, 9.5, 2.2],
State: [NY, TX, FL, AL, AK, TX, TX]
,
index=[Jane, Nick, Aaron, Penelope, Dean,
Christina, Cornelia])

print(df.dtypes)

Output:

Age         int64
Color object
Food object
Height int64
Score float64
State object
dtype: object

28更改 DataFrame 指定列的数据类型

import pandas as pd

df = pd.DataFrame(Age: [30, 20, 22, 40, 32, 28, 39],
Color: [Blue, Green, Red, White, Gray, Black,
Red],
Food: [Steak, Lamb, Mango, Apple, Cheese,
Melon, Beans],
Height: [165, 70, 120, 80, 180, 172, 150],
Score: [4.6, 8.3, 9.0, 3.3, 1.8, 9.5, 2.2],
State: [NY, TX, FL, AL, AK, TX, TX]
,
index=[Jane, Nick, Aaron, Penelope, Dean,
Christina, Cornelia])

print(df.dtypes)

df[Age] = df[Age].astype(str)

print(df.dtypes)

Output:

Age         int64
Color object
Food object
Height int64
Score float64
State object
dtype: object
Age object
Color object
Food object
Height int64
Score float64
State object
dtype: object

29如何将列的数据类型转换为 DateTime 类型

import pandas as pd

df = pd.DataFrame(DateOFBirth: [1349720105, 1349806505, 1349892905,
1349979305, 1350065705, 1349792905,
1349730105],
State: [NY, TX, FL, AL, AK, TX, TX]
,
index=[Jane, Nick, Aaron, Penelope, Dean,
Christina, Cornelia])

print("\\n----------------Before---------------\\n")
print(df.dtypes)
print(df)

df[DateOFBirth] = pd.to_datetime(df[DateOFBirth], unit=s)

print("\\n----------------After----------------\\n")
print(df.dtypes)
print(df)

Output:

----------------Before---------------

DateOFBirth int64
State object
dtype: object
DateOFBirth State
Jane 1349720105 NY
Nick 1349806505 TX
Aaron 1349892905 FL
Penelope 1349979305 AL
Dean 1350065705 AK
Christina 1349792905 TX
Cornelia 1349730105 TX

----------------After----------------

DateOFBirth datetime64[ns]
State object
dtype: object
DateOFBirth State
Jane 2012-10-08 18:15:05 NY
Nick 2012-10-09 18:15:05 TX
Aaron 2012-10-10 18:15:05 FL
Penelope 2012-10-11 18:15:05 AL
Dean 2012-10-12 18:15:05 AK
Christina 2012-10-09 14:28:25 TX
Cornelia 2012-10-08 21:01:45 TX

30将 DataFrame 列从 floats 转为 ints

import pandas as pd

df = pd.DataFrame(DailyExp: [75.7, 56.69, 55.69, 96.5, 84.9, 110.5,
58.9],
State: [NY, TX, FL, AL, AK, TX, TX]
,
index=[Jane, Nick, Aaron, Penelope, Dean,
Christina, Cornelia])

print("\\n----------------Before---------------\\n")
print(df.dtypes)
print(df)

df[DailyExp] = df[DailyExp].astype(int)

print("\\n----------------After----------------\\n")
print(df.dtypes)
print(df)

Output:

----------------Before---------------

DailyExp float64
State object
dtype: object
DailyExp State
Jane 75.70 NY
Nick 56.69 TX
Aaron 55.69 FL
Penelope 96.50 AL
Dean 84.90 AK
Christina 110.50 TX
Cornelia 58.90 TX

----------------After----------------

DailyExp int32
State object
dtype: object
DailyExp State
Jane 75 NY
Nick 56 TX
Aaron 55 FL
Penelope 96 AL
Dean 84 AK
Christina 110 TX
Cornelia 58 TX

31如何把 dates 列转换为 DateTime 类型

import pandas as pd

df = pd.DataFrame(DateOfBirth: [1986-11-11, 1999-05-12, 1976-01-01,
1986-06-01, 1983-06-04, 1990-03-07,
1999-07-09],
State: [NY, TX, FL, AL, AK, TX, TX]
,
index=[Jane, Nick, Aaron, Penelope, Dean,
Christina, Cornelia])

print("\\n----------------Before---------------\\n")
print(df.dtypes)

df[DateOfBirth] = df[DateOfBirth].astype(datetime64)

print("\\n----------------After----------------\\n")
print(df.dtypes)

Output:

----------------Before---------------

DateOfBirth object
State object
dtype: object

----------------After----------------

DateOfBirth datetime64[ns]
State object
dtype: object

32两个 DataFrame 相加

import pandas as pd

df1 = pd.DataFrame(Age: [30, 20, 22, 40], Height: [165, 70, 120, 80],
Score: [4.6, 8.3, 9.0, 3.3], State: [NY, TX,
FL, AL],
index=[Jane, Nick, Aaron, Penelope])

df2 = pd.DataFrame(Age: [32, 28, 39], Color: [Gray, Black, Red],
Food: [Cheese, Melon, Beans],
Score: [1.8, 9.5, 2.2], State: [AK, TX, TX],
index=[Dean, Christina, Cornelia])

df3 = df1.append(df2, sort=True)

print(df3)

Output:

Age  Color    Food  Height  Score State
Jane 30 NaN NaN 165.0 4.6 NY
Nick 20 NaN NaN 70.0 8.3 TX
Aaron 22 NaN NaN 120.0 9.0 FL
Penelope 40 NaN NaN 80.0 3.3 AL
Dean 32 Gray Cheese NaN 1.8 AK
Christina 28 Black Melon NaN 9.5 TX
Cornelia 39 Red Beans NaN 2.2 TX

33在 DataFrame 末尾添加额外的行

import pandas as pd

employees = pd.DataFrame(
EmpCode: [Emp001, Emp002, Emp003, Emp004, Emp005],
Name: [John, Doe, William, Spark, Mark],
Occupation: [Chemist, Statistician, Statistician,
Statistician, Programmer],
Date Of Join: [2018-01-25, 2018-01-26, 2018-01-26, 2018-02-26,
2018-03-16],
Age: [23, 24, 34, 29, 40])

print("\\n------------ BEFORE ----------------\\n")
print(employees)

employees.loc[len(employees)] = [45, 2018-01-25, Emp006, Sunny,
Programmer]

print("\\n------------ AFTER ----------------\\n")
print(employees)

Output:

------------ BEFORE ----------------

Age Date Of Join EmpCode Name Occupation
0 23 2018-01-25 Emp001 John Chemist
1 24 2018-01-26 Emp002 Doe Statistician
2 34 2018-01-26 Emp003 William Statistician
3 29 2018-02-26 Emp004 Spark Statistician
4 40 2018-03-16 Emp005 Mark Programmer

------------ AFTER ----------------

Age Date Of Join EmpCode Name Occupation
0 23 2018-01-25 Emp001 John Chemist
1 24 2018-01-26 Emp002 Doe Statistician
2 34 2018-01-26 Emp003 William Statistician
3 29 2018-02-26 Emp004 Spark Statistician
4 40 2018-03-16 Emp005 Mark Programmer
5 45 2018-01-25 Emp006 Sunny Programmer

34为指定索引添加新行

import pandas as pd

employees = pd.DataFrame(
data=Name: [John Doe, William Spark],
Occupation: [Chemist, Statistician],
Date Of Join: [2018-01-25, 2018-01-26],
Age: [23, 24],
index=[Emp001, Emp002],
columns=[Name, Occupation, Date Of Join, Age])

print("\\n------------ BEFORE ----------------\\n")
print(employees)

employees.loc[Emp003] = [Sunny, Programmer, 2018-01-25, 45]

print("\\n------------ AFTER ----------------\\n")
print(employees)

Output:

------------ BEFORE ----------------

Name Occupation Date Of Join Age
Emp001 John Doe Chemist 2018-01-25 23
Emp002 William Spark Statistician 2018-01-26 24

------------ AFTER ----------------

Name Occupation Date Of Join Age
Emp001 John Doe Chemist 2018-01-25 23
Emp002 William Spark Statistician 2018-01-26 24
Emp003 Sunny Programmer 2018-01-25 45

35如何使用 for 循环添加行

import pandas as pd

cols = [Zip]
lst = []
zip = 32100

for a in range(10):
lst.append([zip])
zip = zip + 1

df = pd.DataFrame(lst, columns=cols)

print(df)

Output:

Zip
0 32100
1 32101
2 32102
3 32103
4 32104
5 32105
6 32106
7 32107
8 32108
9 32109

36在 DataFrame 顶部添加一行

import pandas as pd

employees = pd.DataFrame(
EmpCode: [Emp002, Emp003, Emp004],
Name: [John, Doe, William],
Occupation: [Chemist, Statistician, Statistician],
Date Of Join: [2018-01-25, 2018-01-26, 2018-01-26],
Age: [23, 24, 34])

print("\\n------------ BEFORE ----------------\\n")
print(employees)

# New line
line = pd.DataFrame(Name: Dean, Age: 45, EmpCode: Emp001,
Date Of Join: 2018-02-26, Occupation: Chemist
, index=[0])

# Concatenate two dataframe
employees = pd.concat([line,employees.ix[:]]).reset_index(drop=True)

print("\\n------------ AFTER ----------------\\n")
print(employees)

Output:

------------ BEFORE ----------------

Age Date Of Join EmpCode Name Occupation
0 23 2018-01-25 Emp002 John Chemist
1 24 2018-01-26 Emp003 Doe Statistician
2 34 2018-01-26 Emp004 William Statistician

------------ AFTER ----------------

Age Date Of Join EmpCode Name Occupation
0 45 2018-02-26 Emp001 Dean Chemist
1 23 2018-01-25 Emp002 John Chemist
2 24 2018-01-26 Emp003 Doe Statistician
3 34 2018-01-26 Emp004 William Statistician

37如何向 DataFrame 中动态添加行

import pandas as pd

df = pd.DataFrame(columns=[Name, Age])

df.loc[1, Name] = Rocky
df.loc[1, Age] = 23

df.loc[2, Name] = Sunny

print(df)

Output:

Name  Age
1 Rocky 23
2 Sunny NaN

38在任意位置插入行

import pandas as pd

df = pd.DataFrame(columns=[Name, Age])

df.loc[1, Name] = Rocky
df.loc[1, Age] = 21

df.loc[2, Name] = Sunny
df.loc[2, Age] = 22

df.loc[3, Name] = Mark
df.loc[3, Age] = 25

df.loc[4, Name] = Taylor
df.loc[4, Age] = 28

print("\\n------------ BEFORE ----------------\\n")
print(df)

line = pd.DataFrame("Name": "Jack", "Age": 24, index=[2.5])
df = df.append(line, ignore_index=False)
df = df.sort_index().reset_index(drop=True)

df = df.reindex([Name, Age], axis=1)
print("\\n------------ AFTER ----------------\\n")
print(df)

Output:

------------ BEFORE ----------------

Name Age
1 Rocky 21
2 Sunny 22
3 Mark 25
4 Taylor 28

------------ AFTER ----------------

Name Age
0 Rocky 21
1 Sunny 22
2 Jack 24
3 Mark 25
4 Taylor 28

39使用时间戳索引向 DataFrame 中添加行

import pandas as pd

df =

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