从文件中创建嵌套字典

Question

我需要帮助解决一个挑战问题。

假设我们已经使用read方法将文件加载到字符串viscosity_data中。viscosity_data包含数据(按gas、C、T_0、mu_0的顺序排列)，例如：

viscosity_data = '''air,120,291.15,18.27
nitrogen,111,300.55,17.81
oxygen,127,292.25,20.18
carbon dioxide,240,293.15,14.8
carbon monoxide,118,288.15,17.2
hydrogen,72,293.85,8.76
ammonia,370,293.15,9.82
sulphur dioxide,416,293.65,12.54'''

将字符串viscosity_data中的数据转换为嵌套的字典mu_data，这样我们就可以查找C、T0和μ0中的一个名为mu_dataname的气体，其中X可以是'C‘、'T_0’或'mu_0‘之一。mu_data中的数值应该都是浮动的。

例如，以下语句应该是True：

mu_data['air']['C'] == 120.0
mu_data['hydrogen']['T_0'] == 293.85
mu_data['sulphur dioxide']['mu_0'] ==12.54

到目前为止，我还不知道该从哪里出发：

mu_data = {}
#mu_data master
for data in viscosity_data:
    mu_data[name] = viscosity_data

Answer 1

你可以用dict理解来做这件事：

viscosity_data = '''air,120,291.15,18.27
nitrogen,111,300.55,17.81
oxygen,127,292.25,20.18
carbon dioxide,240,293.15,14.8
carbon monoxide,118,288.15,17.2
hydrogen,72,293.85,8.76
ammonia,370,293.15,9.82
sulphur dioxide,416,293.65,12.54'''

viscosity_data = [air_data.split(",") for air_data in viscosity_data.split("\n")]
mu_data = {air_name:{"c": c, "T_0": T_0, "mu_0": mu_0} for air_name,c,T_0,mu_0 in viscosity_data}

或者简单地在一行中使用map

mu_data = {air_name:{"c": c, "T_0": T_0, "mu_0": mu_0} for air_name,c,T_0,mu_0 
           in map(lambda x: x.split(","), viscosity_data.split("\n"))}

输出

{'air': {'T_0': '291.15', 'c': '120', 'mu_0': '18.27'},
 'ammonia': {'T_0': '293.15', 'c': '370', 'mu_0': '9.82'},
 'carbon dioxide': {'T_0': '293.15', 'c': '240', 'mu_0': '14.8'},
 'carbon monoxide': {'T_0': '288.15', 'c': '118', 'mu_0': '17.2'},
 'hydrogen': {'T_0': '293.85', 'c': '72', 'mu_0': '8.76'},
 'nitrogen': {'T_0': '300.55', 'c': '111', 'mu_0': '17.81'},
 'oxygen': {'T_0': '292.25', 'c': '127', 'mu_0': '20.18'},
 'sulphur dioxide': {'T_0': '293.65', 'c': '416', 'mu_0': '12.54'}}

Answer 2

你有一个csv。您应该使用内置的csv模块来解析它：

>>> with io.StringIO(viscosity_data) as f:
...     reader = csv.reader(f)
...     names = 'C','T_0','mu_0'
...     data = {}
...     for gas, *rest in reader:
...         data[gas] = dict(zip(names, map(float,rest)))
...

其结果是：

>>> from pprint import pprint
>>> pprint(data)
{'air': {'C': 120.0, 'T_0': 291.15, 'mu_0': 18.27},
 'ammonia': {'C': 370.0, 'T_0': 293.15, 'mu_0': 9.82},
 'carbon dioxide': {'C': 240.0, 'T_0': 293.15, 'mu_0': 14.8},
 'carbon monoxide': {'C': 118.0, 'T_0': 288.15, 'mu_0': 17.2},
 'hydrogen': {'C': 72.0, 'T_0': 293.85, 'mu_0': 8.76},
 'nitrogen': {'C': 111.0, 'T_0': 300.55, 'mu_0': 17.81},
 'oxygen': {'C': 127.0, 'T_0': 292.25, 'mu_0': 20.18},
 'sulphur dioxide': {'C': 416.0, 'T_0': 293.65, 'mu_0': 12.54}}
>>>

注意，我使用io.StringIO(viscosity_data)来假装字符串viscosity_data实际上是一个文件，但是您应该使用正常的方法打开文件。

也就是说，你应该做：

>>> with opn("my_file.txt") as f:
...     reader = csv.reader(f)
...     names = 'C','T_0','mu_0'
...     data = {}
...     for gas, *rest in reader:
...         data[gas] = dict(zip(names, map(float,rest)))
...

Answer 3

选项1

使用纯python方法(没有任何外部包)。

data = {}
names = ['C', 'T_0', 'mu_0']
for line in viscosity_data.splitlines():
    i, *j  = line.split(',')
    data[i] = dict(zip(names, j))

选项2

使用pandas

如果你用熊猫，这真的很容易。如果你没有它，你可以安装它：

​

pip install pandas

​

import pandas as pd
import io

df = pd.read_csv(io.StringIO(viscosity_data), 
            header=None, names=['gas', 'C', 'T_0', 'mu_0'])
data = df.set_index('gas').to_dict('i')