How to write an input asking the user to type using both letters and numbers?

I am writing a line where I ask the user to input their school ID, which requires both letters and numbers. How can I do this? When I input a number as my answer when asked, my program works. If I type a letter with the number I get the error.
Here is my code thus far using Python 3.6 IDLE: def main():

def main():

#Introduction
print ("Welcome to my program!n")

#Variables with starting values waiting for user input

studentid = ""
gpa = 0.0
classnumber = ""

#Prompt for studentID
studentid = eval(input("Please enter your student ID: "))
#Prompt for GPA
gpa = eval(input("Please enter your GPA: "))
#Prompt for classnumber
classnumber = eval(input("Please enter your class information:"))

#display the users information
#StudentID: C100556789
#GPA: 4.0
#Class: COP1000

print ("nStudent ID:t", studentid)
print ("GPA:t", gpa)
print ("Class information:t", classnumber)


And here is my error:

Type "copyright", "credits" or "license()" for more information.
>>> RESTART: C:UsersRene DelgadoDocumentsSchoolFall 2018School CodeStudent Program.py
>>> main() Welcome to my program!

Please enter your student ID: C100556789 Traceback (most recent call
last): File "<pyshell#0>", line 1, in <module>
main() File "C:UsersRene DelgadoDocumentsSchoolFall 2018School CodeStudent Program.py", line 18, in main
studentid = eval(input("Please enter your student ID: ")) File "<string>", line 1, in <module> NameError: name 'C100556789' is not
defined


1 Answer
1

input returns a string that the user inputs, which is what you want already. You should not use eval to evaluate the string as a Python expression, which would generate an error for an input with letters because Python would interpret it as a variable name that does not exist. Simply remove calls to eval and your code would work:

input

eval

eval

#Prompt for studentID
studentid = input("Please enter your student ID: ")
#Prompt for GPA
gpa = input("Please enter your GPA: ")
#Prompt for classnumber
classnumber = input("Please enter your class information:")


Note that if you want to treat gpa as a number for numeric operations, you should also convert the input to a floating number with float():

gpa

float()

gpa = float(input("Please enter your GPA: "))


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