name 'temperatures' not defined?

[johnhall83]

I get an error saying, print('The input list is:', temperatures)
NameError: name 'temperatures' is not defined

This is my code:

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#initialise the input_list with the given values   #initialise the output_list to the empty list def get_input():     temperatures = get_input()     input_list = list(         map(float, input("\nEnter the temperatures:").strip().split())) #if the input_value satisfies the condition:     return input_list     temperatures = get_input()     output_list = []     for i in temperatures:         if i > 0.0 and i < 5.0:             point = 0 # append the input_value to the output_list     else:             output_list.append(i) # print the output_list print('The input list is:', temperatures) print('The output list is:', output_list)

How do I define Temperatures?
The table is,

Input Output
[4.7] []
[5.2] [5.2]
[0, 3, 5, 7, 5, 4, 2, 0, -0.2]. [7,-0.2]

[catosp]

try this:

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def get_input():     input_list = list(         map(float, input("\nEnter the temperatures:").strip().split()))     return input_list       temperatures = get_input() output_list = [] for i in temperatures:     if i > 0.0 and i < 5.0:         point = 0     else:         output_list.append(i)     print('The input list is:', temperatures) print('The output list is:', output_list)

[DreamingInsanity]

You could do something like this:

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import ast   def get_input():     input_list = ast.literal_eval(input("\nEnter the temperatures: "))     return input_list   def get_temperature(temps):   output_list = []   for t in temps:     if t >= 0 and t <= 5:       pass     else:       output_list.append(t)       return output_list   input_list = get_input() output_list = get_temperature(input_list) print('The input list is: ', input_list) print('The output list is: ', output_list)

The "ast" library is there so you can convert a string representation of a list like "[0, 4, 5]" into an actual list like [0, 4, 5]. It is also safer than eval().

The way you had yours set up would have caused recursion because you were calling the function from within itself.

[deanhystad]

The concept of "scope" is very important in Python. Modules (files) define a scope. Functions define a scope. Classes define a scope. When you see the message "X is not defined" it is often a matter of scope.

In your example "temperatures" is defined inside the scope of function get_input(). The print statements at the bottom of the module are outside the get_input() function's scope and cannot see "temperatures".

You could fix this by defining "temperatures in the module scope.

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temperatures = []  # defines temperatures in module scope def get_input():     global temperatures # Use temperatures from module scope     temperatures =  map(float, input("\nEnter the temperatures:").strip().split()))   print(temperatures)

Globals work ok when used sparingly, but there is no way to tell where the global variable is modified other than reading the code. Ok for 1 variable in a 50 line program, but tedious for many variables in a 1000 line module.

To make code easier to understand/read/debug the relationship between variable and modifier should be direct. Some variables can be passed as arguments to a function that then modifies the variable. This only works for mutable types like lists and dictionaries, and not for immutable types like numbers and strings. This would works (somewhat).

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def get_input(temperatures):         temperatures = list(map(float, input("\nEnter the temperatures:").strip().split()))   temperatures = [] get_input(temperatures) print(temperatures)

Modifying arguments inside a funtion is frowned upon, because as with global variables the only way to know if a variable gets modified is to read the code. At least you don't have to search the entire file.

The best way to associate modification of a variable with a function call is to make the variable the return value. In this example there is no doubt that the function "get_input" modifies "temperatures".

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def get_input():         return list(map(float, input("\nEnter the temperatures:").strip().split()))   temperatures = get_input() print(temperatures)

And if you have more than one return value, that isn't a problem in Python.

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def get_input(minTemp, maxTemp):         alltemps = list(map(float, input("\nEnter the temperatures:").strip().split()))         in_range = [x for x in alltemps if minTemp <= x <= maxTemp]         return alltemps, in_range   temperatures, temperate = get_input(12, 20) print(temperatures) print(temperate)