Day 18 [Python ML、Pandas] 重新命名和整合

import pandas as pd
reviews = pd.read_csv("./winemag-data-130k-v2.csv", index_col=0)
pd.set_option('max_rows', 5)

Renaming

若要更新column的name

可以用rename function

rename(columns=({'points':'score'}))，可将points替换成score

reviews.rename(columns=({'points':'score'}))

.dataframe tbody tr th {
    vertical-align: top;
}

.dataframe thead th {
    text-align: right;
}

若要对index做更新，则将rename中的column更改为index

rename(index={0:'firstEntry', 1:'secondEntry'})

reviews.rename(index={0:'firstEntry', 1:'secondEntry'})

.dataframe tbody tr th {
    vertical-align: top;
}

.dataframe thead th {
    text-align: right;
}

row和column都会有自己的attribute name

可以使用rename_axis替换掉row和column的name

reviews.rename_axis("wines", axis='rows').rename_axis("fields", axis='columns')

.dataframe tbody tr th {
    vertical-align: top;
}

.dataframe thead th {
    text-align: right;
}

Combining

在pandas中有3个主要合并DataFrame和Series的funciton

concat、merge、join，merge做的事和join很像，因此先忽略这个function

concat

concat可以将dataframe向下合并，若要忽略index，可使用ignore_index = True parameter

canadian_youtube = pd.read_csv('./CAvideos.csv')
british_youtube = pd.read_csv('./GBvideos.csv')

pd.concat([canadian_youtube, british_youtube])

.dataframe tbody tr th {
    vertical-align: top;
}

.dataframe thead th {
    text-align: right;
}

若要左右合并dataframe，可使用join()函式

会根据相同的index对资料做合并

left = canadian_youtube.set_index(['title', 'trending_date'])
right = british_youtube.set_index(['title', 'trending_date'])

left.join(right, lsuffix='_CAN', rsuffix='_UK')

.dataframe tbody tr th {
    vertical-align: top;
}

.dataframe thead th {
    text-align: right;
}