Aligning text according to user input in python

Question

aStr = input("Enter a string message: ")
fW = eval(input("Enter a positive integer: "))
print(f"Right aligned is <{aStr:>fW}>")

so, this is my code, I would like to align the spaces according to the user input. Whenever I try to use eval or int in fW, it shows this error.

Traceback (most recent call last):
  File "C:\Users\vmabr\Downloads\A1Q2.py", line 5, in <module>
    print(f"Right aligned is <{aStr:fW}>")
ValueError: Invalid format specifier

May I know what's the fix?

try: aStr = input("Enter a string message: ") fW = int(input("Enter a positive integer: ")) print(f"Right aligned is <{aStr.rjust(fW)}>") — Byron
– Byron, Commented Oct 17, 2022 at 12:49
Before you learn anything else, you should unlearn that the eval function exists. eval is not safe to use, especially on unsanitized user input as you have done. See stackoverflow.com/q/1832940/843953 — pho
– pho, Commented Oct 18, 2022 at 5:39
Oh, I didn't know that. My professor was the one who recommended me to use eval so I just followed. Thank you very much for letting me know — completenewbie001
– completenewbie001, Commented Oct 19, 2022 at 12:23

Christian Karcher · Accepted Answer · 2022-10-18 08:15:34Z

3

You were close. To implement a "parameterized" format-string, you need to wrap the parameter fW into additional curly braces:

aStr = input("Enter a string message: ")
fW = int(input("Enter a positive integer: "))
print(f"Right aligned is <{aStr:>{fW}}>")  # {fW} instead of fW

See PEP 498 -> format specifiers for further information.

edited Oct 18, 2022 at 8:15

answered Oct 18, 2022 at 5:28

Christian Karcher

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1 Comment

completenewbie001 Over a year ago

Thank you so much! It works like magic! Curse these curly brackets . . . Oh and also thanks for the link, I will definitely check it out.

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