從 Pandas DataFrame 系列中獲取列表
Luqman Khan
2022年5月16日
Python 是一種眾所周知的資料分析語言，主要歸功於 Python 包。Pandas 是幫助我們更輕鬆地分析資料的軟體包之一。
Pandas tolist() 方法將系列轉換為 Python 的系列或內建列表。預設情況下，series 是 pandas.core.series.Series 資料型別和 tolist() 方法的型別，轉換為資料列表。
使用 tolist() 方法從 Pandas DataFrame 系列中獲取列表
本文將討論如何從 Pandas Dataframe 列中獲取列表。我們將首先將 CSV 檔案讀入 Pandas DataFrame。
import pandas as pd
# read csv file
df = pd.read_csv("home_price.csv")
# display 3 rows
df = df.head(3)
print(df)
輸出：
Area Home price
0 1000 10000
1 1200 12000
2 1300 13000
現在我們將從列中提取值並將其轉換為列表，因為我們知道 tolist() 有幫助。
list1 = df["Home price"].values.tolist()
print("extract the value of series and converting into the list")
print(list1)
輸出：
extract the value of series and converting into the list
[10000, 12000, 13000, 14000, 15000]
列表是一個有序且靈活的 Python 容器，是 Python 中最常見的資料結構之一。元素被插入方括號 []，用逗號分隔以建立一個列表。列表可以包含重複值；這就是我們主要在資料集中使用列表的原因。
import numpy as np
import pandas as pd
# read csv file
df = pd.read_csv("home_price.csv")
# extract the value of series and converting into the list
list1 = df["Home price"].values.tolist()
list1 = np.array(list1)
# type casting in list data type
updated = list(list1 * 1.5)
print("after include 1.5 % tax\n")
print(updated, "new home price")
df["Home price"] = updated
# create new csv
df.to_csv("home prices after 1 year.csv")
df2 = pd.read_csv("home prices after 1 year.csv")
print(df2)
在這種情況下，當前價格會增加 1.5 稅。現在我們建立一個名為 updated 的列表並更新現有列；此外，我們使用 to_csv() 方法建立一個新的 CSV 檔案。
輸出：
after include 1.5 % tax
[15000.0, 18000.0, 19500.0, 21000.0, 22500.0] new home price
Unnamed: 0 Area Home price
0 0 1000 15000.0
1 1 1200 18000.0
2 2 1300 19500.0
3 3 1400 21000.0
4 4 1500 22500.0
讓我們考慮另一個簡單的例子：
import pandas as pd
df = pd.DataFrame(
{
"Country": ["Pakistan", "India", "America", "Russia", "China"],
"Immigrants": ["2000", "2500", "6000", "4000", "1000"],
"Years": ["2010", "2008", "2011", "2018", "2016"],
}
)
print(df, "\n")
list = df.columns.tolist()
print(type(df.columns))
print("\n", list, "\n")
print("After type cast into the list")
print(type(list))
請注意，系列資料型別被 tolist() 改變了，我們得到了一個包含 Dataframe 所有列的列表。
輸出：
Country Immigrants Years
0 Pakistan 2000 2010
1 India 2500 2008
2 America 6000 2011
3 Russia 4000 2018
4 China 1000 2016
<class 'pandas.core.indexes.base.Index'>
['Country', 'Immigrants', 'Years']
After type cast into the list
<class 'list'>
所有的程式碼都在這裡。
import numpy as np
import pandas as pd
# read csv file
df = pd.read_csv("home_price.csv")
# display 3 rows
df = df.head(3)
print(df)
list1 = df["Home price"].values.tolist()
print("extract the value of series and converting into the list")
print(list1)
# another example
# read csv file
df = pd.read_csv("home_price.csv")
# extract the value of series and converting into the list
list1 = df["Home price"].values.tolist()
list1 = np.array(list1)
# type casting in list data type
updated = list(list1 * 1.5)
print("after include 1.5 % tax\n")
print(updated, "new home price")
df["Home price"] = updated
# create new csv
df.to_csv("home prices after 1 year.csv")
df2 = pd.read_csv("home prices after 1 year.csv")
print(df2)
# another example
df = pd.DataFrame(
{
"Country": ["Pakistan", "India", "America", "Russia", "China"],
"Immigrants": ["2000", "2500", "6000", "4000", "1000"],
"Years": ["2010", "2008", "2011", "2018", "2016"],
}
)
print(df, "\n")
list = df.columns.tolist()
print(type(df.columns))
print("\n", list, "\n")
print("After type cast into the list")
print(type(list))
輸出：
Area Home price
0 1000 10000
1 1200 12000
2 1300 13000
extract the value of series and converting into the list
[10000, 12000, 13000]
after include 1.5 % tax
[15000.0, 18000.0, 19500.0, 21000.0, 22500.0] new home price
Unnamed: 0 Area Home price
0 0 1000 15000.0
1 1 1200 18000.0
2 2 1300 19500.0
3 3 1400 21000.0
4 4 1500 22500.0
Country Immigrants Years
0 Pakistan 2000 2010
1 India 2500 2008
2 America 6000 2011
3 Russia 4000 2018
4 China 1000 2016
<class 'pandas.core.indexes.base.Index'>
['Country', 'Immigrants', 'Years']
After type cast into the list
<class 'list'>