擅长:python、mysql、java
<p>您需要:</p>
<pre><code>temp = df[['col_a','col_b','col_c','col_d']].eq("a").sum(axis=1)
print(temp)
v = []
for i in temp:
a_col = "a"*i
v.append(a_col)
df['col_a'] = v
df['col_b'] = 'b'
df['col_c'] = 'c'
df['col_d'] = 'd'
df.drop(['ex_1','ex_2','ex_3'],1,inplace=True)
print(df)
</code></pre>
<p>输出:</p>
^{pr2}$