NameError：名称“`Timevalue`”未定义

Question

I store data in csv file as follwing:

row = dict_items([('Time ': '2017-12-01T13:54:04'), ('Energy [kWh]': '0.01'), ('Voltage [V]': '221.64'), ('Current [A]': '0.08')])

Now i want to store it like that:

('Time ': '2017-12-01T13:54:04', 'Energy [kWh]': '0.01'),
('Time ': '2017-12-01T13:54:04','Voltage [V]': '221.64'), 
('Time ': '2017-12-01T13:54:04','Current [A]': '0.08')])

so i wrote this code bellow and i define

    Device=""
    Value=""
    for key, value in row.items():
        print(row.items())
        if key == 'Time':
            Timevalue = value
            print(Zeitvalue)
        Device = key
        Value = value
        doc = {'Device':Device, 'Measure':Value , 'Time':Timevalue }

i got this error: NameError: name ' Timevalue ' is not defined How can i make the Timevalue variable globale to avoid this Problem? Thank you

Answer 1

That ('Time ': '2017-12-01T13:54:04', 'Energy [kWh]': '0.01') syntax is not valid Python. Assuming you actually want a list of dictionaries, it's not too hard to perform that conversion.

You first need to grab the time stamp so it can be combined with each of the other items, and then you can drop it from the dict to make it easier to copy the remaining items to the new structure. Note that this modifies the original dict passed to the function. If you don't want that, you can either make a copy of the passed-in dict, or put an if test in the loop that copies the data to the new structure so that the time item is skipped.

def convert(old):
    time_key = 'Time '
    # Save the time
    time_item = (time_key, old[time_key])
    # Add remove it
    del old[time_key]
    # Copy remaining items to new dicts and save them in a list
    return [dict([time_item, item]) for item in old.items()]

row = {
    'Time ': '2017-12-01T13:54:04', 
    'Energy [kWh]': '0.01', 
    'Voltage [V]': '221.64', 
    'Current [A]': '0.08',
}

new_data = convert(row)
for d in new_data:
    print(d)

output

{'Time ': '2017-12-01T13:54:04', 'Energy [kWh]': '0.01'}
{'Time ': '2017-12-01T13:54:04', 'Voltage [V]': '221.64'}
{'Time ': '2017-12-01T13:54:04', 'Current [A]': '0.08'}

---

Here's how to do it if you don't want to mutate or copy the original dict:

def convert(old):
    time_key = 'Time '
    # Save the time
    time_item = (time_key, old[time_key])
    # Copy other items to new dicts and save them in a list
    return [dict([time_item, (key, val)]) 
        for key, val in old.items() if key != time_key]

Note that this is less efficient because it has to test every key to ensure it's not the time key.

---

To save the data in a list of OrderedDict s, we need to change the logic slightly. We also need to create the OrderedDict s properly so that the items are in the desired order.

from collections import OrderedDict
from pprint import pprint

def convert(row):
    time_key = 'Time '
    time_value = row[time_key]
    new_data = []
    for key, val in row.items():
        if key == time_key:
            continue
        new_data.append(OrderedDict(Device=key, Measure=val, Time=time_value))
    return new_data

row = {
    'Time ': '2017-12-01T13:54:04', 'Energy [kWh]': '0.01',
    'Voltage [V]': '221.64', 'Current [A]': '0.08'
}

new_data = convert(row)
pprint(new_data)

output

[OrderedDict([('Device', 'Energy [kWh]'),
              ('Measure', '0.01'),
              ('Time', '2017-12-01T13:54:04')]),
 OrderedDict([('Device', 'Voltage [V]'),
              ('Measure', '221.64'),
              ('Time', '2017-12-01T13:54:04')]),
 OrderedDict([('Device', 'Current [A]'),
              ('Measure', '0.08'),
              ('Time', '2017-12-01T13:54:04')])]