在浮点数python之前插入逗号

Question

我是python的新手。我有一个string，看起来如下：

a= "1.1 Introduction 1.2 Inverse of a Non-Singular 1.3 Elementary Transformations  1.4 Applications 1.5 Applications of Matrices"

我希望在String中的数字之前插入逗号

我尝试过的代码：

a= "1.1 Introduction 1.2 Inverse of a Non-Singular 1.3 Elementary Transformations  1.4 Applications 1.5 Applications of Matrices"
b = ""
for i in a:
print(i)
try: 
temp = int(i)
b = b+ ","+ temp
except:
b = b + i

但这是错误的。请帮我解决一些问题。

所需输出：

"1.1 Introduction, 1.2 Inverse of a Non-Singular, 1.3 Elementary Transformations,  1.4 Applications, 1.5 Applications of Matrices"

Answer 1

这可能会有所帮助：

import re
a= "10.1 Introduction 10.2 Inverse of a Non-Singular 1.3 Elementary Transformations  1.4 Applications 1.5 Applications of Matrices"
re.sub(r"s+(d+.d+)", r", 1", a)