Initializing variables in python

Question

Even though initializing variables in python is not necessary  my professor still wants us to do it for practice  I wrote my program and it worked fine  but after I tried to initialize some of the variables I got an error message when I tried to run it  Here is the first part of my program   def main         grade 1  grade 2  grade 3  average   0 0     year   0      fName  lName  ID  converted ID          infile   open  studentinfo txt    r       data   infile read       fName  lName  ID  year   data split          year   int year         Prompt the user for three test scores      grades   eval input  Enter the three test scores separated by a comma             Create a username      uName    lName  4    fName  2    str year   lower       converted id   ID  3     -    ID 3 5     -    ID 5       grade 1  grade 2  grade 3   grades   The error message   grade 1  grade 2  grade 3  average   0 0  TypeError   float  object is not iterable

User · Answer

There are several ways to assign the equal variables.

The easiest one:

grade_1 = grade_2 = grade_3 = average = 0.0

With unpacking:

grade_1, grade_2, grade_3, average = 0.0, 0.0, 0.0, 0.0

With list comprehension and unpacking:

>>> grade_1, grade_2, grade_3, average = [0.0 for _ in range(4)]
>>> print(grade_1, grade_2, grade_3, average)
0.0 0.0 0.0 0.0

User · Answer

You are asking to initialize four variables using a single float object  which of course is not iterable  You can do -   grade 1  grade 2  grade 3  grade 4    0 0 for   in range 4   grade 1   grade 2   grade 3   grade 4   0 0   Unless you want to initialize them with different values of course

User · Answer

I know you have already accepted another answer  but I think the broader issue needs to addressed - programming style that is suitable to the current language   Yes   initialization  isn t needed in Python  but what you are doing isn t  initialization  It is just an incomplete and erroneous imitation of initialization as practiced in other languages  The important thing about initialization in static typed languages is that you specify the nature of the variables     In Python  as in other languages  you do need to give variables values before you use them   But giving them values at the start of the function isn t important  and even wrong if the values you give have nothing to do with values they receive later  That isn t  initialization   it s  reuse    I ll make some notes and corrections to your code   def main         doc to define the function      proper Python indentation      document significant variables  especially inputs and outputs      grade 1  grade 2  grade 3  average - id these      year - id this      fName  lName  ID  converted ID      infile   open  studentinfo txt    r         you didn t  intialize  this variable     data   infile read          nor this       fName  lName  ID  year   data split           this will produce an error if the file does not have the right number of strings       year  is now a string  even though you  initialized  it as 0     year   int year       now  year  is an integer      a language that requires initialization would have raised an error      over this switch in type of this variable        Prompt the user for three test scores    grades   eval input  Enter the three test scores separated by a comma            eval  ouch       you could have handled the input just like you did the file input      grade 1  grade 2  grade 3   grades         this would work only if the user gave you an  iterable  with 3 values      eval   doesn t ensure that it is an iterable      and it does not ensure that the values are numbers        What would happen with this user input    one   two   three  4         Create a username     uName    lName  4    fName  2    str year   lower       converted id   ID  3     -    ID 3 5     -    ID 5        earlier you  initialized  converted ID      initialization in a static typed language would have caught this typo      pseudo-initialization in Python does not catch typos

User · Answer

The issue is in the line -  grade 1  grade 2  grade 3  average   0 0   and  fName  lName  ID  converted ID        In python  if the left hand side of the assignment operator has multiple variables  python would try to iterate the right hand side that many times and assign each iterated value to each variable sequentially   The variables grade 1  grade 2  grade 3  average need three 0 0 values to assign to each variable   You may need something like -  grade 1  grade 2  grade 3  average    0 0 for   in range 4   fName  lName  ID  converted ID       for   in range 4

User · Answer

def grade inlist       grade 1  grade 2  grade 3  average  inlist     print  grade 1      print  grade 2   mark  1 2 3 4  grade mark

User · Answer

If you want to use the destructuring assignment  you ll need the same number of floats as you have variables   grade 1  grade 2  grade 3  average   0 0  0 0  0 0  0 0

User · Answer

Python treats comma on the left hand side of equal sign       as an input splitter  Very useful for functions that return a tuple   e g   x y    5 2    What you want to do is   grade 1   grade 2   grade 3   average   0 0   though that might not be the most clear way to write it

[python] "Initializing" variables in python?

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