Python 替换单元格中的字符

我有以下数据帧：

df = pd.DataFrame(columns=["a","b","c"])
df.loc[1] = [1,2,3]
df.loc[2] = ["123.12", "3455,435",0]
df.loc[3] = [23.2, 55.5,0.1]
df.loc[4] = ["1,3","3,5","7.8"]

我想用点（“.”）替换所有逗号（“，”），结果如下：

df = pd.DataFrame(columns=["a","b","c"])
df.loc[1] = [1,2,3]
df.loc[2] = ["123.12", "3455.435",0]
df.loc[3] = [23.2, 55.5,0.1]
df.loc[4] = ["1.3","3.5","7.8"]

我该怎么做？到目前为止，我使用了pandas replace函数，但它不起作用

与

regex=True一起使用

替换子字符串：

df = df.replace(',','.', regex=True)
print (df)
        a         b    c
1       1         2    3
2  123.12  3455.435    0
3    23.2      55.5  0.1
4     1.3       3.5  7.8