> For the complete documentation index, see [llms.txt](https://meetbill.gitbook.io/butterfly-user-doc/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://meetbill.gitbook.io/butterfly-user-doc/best_practices/code_practice.md).

# Code practice

## 1 Python

### 1.1 避免魔术数字

不要在代码中出现 [Magic Number](https://en.wikipedia.org/wiki/Magic_number_\(programming\))

```
# BAD
if cluster_type == 1:
    pass


# GOOD
class enum_cluster_type(object):
    """"""
    K8S = 1
    Mesos = 2

if cluster_type == enum_cluster_type.K8S:
    pass
```

### 1.2 不要预计算字面量表达式

如果某个变量是通过简单算式得到的，应该保留算式内容。不要直接使用计算后的结果。

```
# BAD
if delta_seconds > 950400:
    return

# GOOD
if delta_seconds > 11 * 24 * 3600:
    return
```

### 1.3 优先使用列表推导或内联函数

使用列表推导或内联函数能够清晰知道要生成一个列表，并且更简洁

```
# BAD
list_two = []
for v in list_one:
    if v[0]:
        new_list.append(v[1])

# GOOD one
list_two = [v[1] for v in list_one if v[0]]

# GOOD two
list_two = list(filter(lambda x: x[0], list_one))
```

### 1.4 当在**非测试**代码中使用 `assert` 时，妥善添加断言信息

```python
>>> assert 1 == 0
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AssertionError
```

在大段的日志中，单独存在的 `AssertionError` 不利于日志检索和问题定位，所以添加上可读的断言信息是更推荐的做法。

```python
# BAD
assert "hello" == "world"

# GOOD
assert "hello" == "world", "Hello is not equal to world"
```

> eg:

```
assert isinstance(req, Request), "req must request"
```

## 2 Butterfly

### 2.1 command 执行时默认展示 table，接口请求时展示 json

参数默认值设置为 "table"，程序内部判断当前请求方式

```
if req.wsgienv.get("REQUEST_METHOD", "COMMAND") != "COMMAND":
    display = "json"
```