将python与knitr一起使用

Question

我想和knitr一起使用python。但是，python块似乎单独进行评估，并且变量定义在块之间丢失。

如何解决这个问题？

最小例子：

test.pymd

---
title: "Minimal example"
---

With a print statement.

```{r hello}
x = 'Hello, Python World!'
print(x)
```

Without a print statement.

```{r world}
print(x)
```

test.md

---
title: "Minimal example"
---

With a print statement.


```python
x = 'Hello, Python World!'
print(x)
```

```
Hello, Python World!
```

Without a print statement.


```python
print(x)
```

```
Traceback (most recent call last):
  File "<string>", line 1, in <module>
NameError: name 'x' is not defined
```

knit2py.r

#! /usr/bin/Rscript --vanilla

args <- commandArgs(TRUE)

if(length(args) < 1) {
    message("Need arguments in the format: %.pymd [%.md]")
    q(status=1)
}

name <- substr(args[1],1,nchar(args[1])-4)

if(length(args) < 2) {
    args[2] <- paste0(name,".md")
}

library(knitr)
opts_chunk$set(engine = 'python')

res <- try(knit(args[1], args[2]))

if(inherits(res, "try-error")) {
    message("Could not successfully knit RMD (or PYMD) to MD")
    q(status=1)
} else q()

现在运行：

./knit2py.r test.pymd test.md 

Answer 1

是的，确实，knitr目前无法评估除R以外的语言的多个块的代码。解决方案不是使用knitr而是使用pweave。对源文件的修改很少：

test.mdw

---
title: "Minimal example"
---

With a print statement.

<<>>=
x = 'Hello, Python World!'
print(x)
@

Without a print statement.

<<>>=
print(x)
@

The end.

现在运行：

pweave -f pandoc test.mdw

pweave网站上有一条说明，使用python3安装将失败。但是，当我只是跑步时，我没有任何问题：

pip install pweave
pip install markdown

也许，这只是一个旧笔记。

Answer 2

这是在knittr块内运行python代码的两种方法的简单示例：

---
title: "Works with python"
output: github_document
---

Does **knitr** work with Python? Use the chunk option `engine='python'`:

```{r engine='python'}
x = 'hello, python world!'
print(x)
print(x.split(' '))
```

Or use the syntax ```` ```{python} ````:

```{python}
x = 'hello, python world!'
print(x.split(' '))
```

我从knittr examples那里得到了