如何在python中使用if else语句的for循环结果中创建一个新变量？

Question

I have these temperatures:

temperatures = [-5.4, 1.0, -1.3, -4.8, 3.9, 0.1, -4.4]

This works as a statement, but I can't get this in to a variable:

for i in temperatures:
if i < -2:
    print('Cold')
elif i >= -2 and i <= 2:
    print('Slippery')
elif i >2 and i < 15:
    print('Comfortable')
else:
    print('Warm') 

I know that the following code works to get a variable from a loop:

x = [i for i in range(21)]
print (x)

So I tried this, but it doesn't work:

temp_class = [i for i in temperatures:
if i < -2:
    print('Cold')
elif i >= -2 and i <= 2:
    print('Slippery')
elif i >2 and i < 15:
    print('Comfortable')
else:
    print('Warm')]

But get this error:

File "", line 1
temp_class = [i for i in temperatures: ^ SyntaxError: invalid syntax

What would be the correct code to: 1. Get a variable from my statement 2. Get both the temperatures and classes in a table similar to a tibble or data.frame in R.

Thanks

Answer 1

If you goal is to get these strings into temp_class just append them instead of print

temperatures = [-5.4, 1.0, -1.3, -4.8, 3.9, 0.1, -4.4]

temp_class = []

for i in temperatures:
    if i < -2:
        temp_class.append('Cold')
    elif i >= -2 and i <= 2:
        temp_class.append('Slippery')
    elif i >2 and i < 15:
        temp_class.append('Comfortable')
    else:
        temp_class.append('Warm')

print(temp_class)
# ['Cold', 'Slippery', 'Slippery', 'Cold', 'Comfortable', 'Slippery', 'Cold']

Answer 2

You can create a function and use it in your list comprehension:

temperatures = [-5.4, 1.0, -1.3, -4.8, 3.9, 0.1, -4.4]

def feeling(temp):
    if temp < -2:
        return 'Cold'
    elif -2 < temp <= 2:
        return 'Slippery'
    elif 2 < temp < 15:
        return 'Comfortable'
    else:
        return 'Warm' 

[feeling(temp) for temp in temperatures]
# ['Cold', 'Slippery', 'Slippery', 'Cold', 'Comfortable', 'Slippery', 'Cold']

Answer 3

Using map()

temperatures = [-5.4, 1.0, -1.3, -4.8, 3.9, 0.1, -4.4]

def get_temp_class(i):
    if i < -2:
        return 'Cold'
    elif i >= -2 and i <= 2:
        return 'Slippery'
    elif i >2 and i < 15:
        return 'Comfortable'
    else:
        return 'Warm'

temp_class = map(get_temp_class, temperatures)