在Pandas中编码列标签以进行机器学习

我正在研究机器学习的汽车评估数据集,数据集是这样的

buying,maint,doors,persons,lug_boot,safety,class
vhigh,vhigh,2,2,small,low,unacc
vhigh,vhigh,2,2,small,med,unacc
vhigh,vhigh,2,2,small,high,unacc
vhigh,vhigh,2,2,med,low,unacc
vhigh,vhigh,2,2,med,med,unacc
vhigh,vhigh,2,2,med,high,unacc

我想将这些字符串按列转换为唯一的枚举整数.我看到pandas.factorize()是要走的路,但它只适用于一列.如何使用一个命令一次性分解数据帧.

我尝试了lambda功能,但它无法正常工作.

df.apply(lambda c:pd.factorize(c),axis = 1)

输出:

   0     ([0, 0, 1, 1, 2, 3, 4], [vhigh, 2, small, low,...

    1     ([0, 0, 1, 1, 2, 3, 4], [vhigh, 2, small, med,...

    2     ([0, 0, 1, 1, 2, 3, 4], [vhigh, 2, small, high...

    3     ([0, 0, 1, 1, 2, 3, 4], [vhigh, 2, med, low, u...

    4       ([0, 0, 1, 1, 2, 2, 3], [vhigh, 2, med, unacc])

    5     ([0, 0, 1, 1, 2, 3, 4], [vhigh, 2, med, high, ...

我看到编码的值,但不能从上面的数组拉出来