Python using int function

Question

I can't run the code below because of the 7th line value = int(qty)*int(price). I can only run it if I use the int() function inside the print() function. Is there a way I can define it's an integer before I ask it to print? The same for float?

file = open("C:\\file.txt","r")
for mid in file:
    qty = mid[38:53]
    qty = qty.lstrip("0")
    price = mid[75:86]
    price = price.lstrip("0")
    value = int(qty)*int(price)
    trades = [qty,price,value]
    print (trades)
file.close()

Shell-->

ValueError: invalid literal for int() with base 10: ''

You can always ask it to be an integer. The string you must be passing may contain letters which make the compiler think its a hexadecimal or have a "." making it a float — cjds, Jul 19 '16 at 19:05
Possible duplicate of [ValueError: invalid literal for int() with base 10: ''](http://stackoverflow.com/questions/1841565/valueerror-invalid-literal-for-int-with-base-10) — lonewaft, Jul 19 '16 at 19:05
either qty or price are not something that can be converted to int. try to print them before the line `value = int(qty)*int(price)` to see whats inside. — Ronen Ness, Jul 19 '16 at 19:06

score 0 · Answer 1 · answered Jul 19 '16 at 19:15

What's happening is that one of your items has either its price or quantity set to 0. When it's read in your code strips that 0 leaving you with an empty string, raising a ValueError when it is converted to an int.

You should probably remove the lstrips. At worst you will get numbers like "04" which the int constructor can handle anyway.

napuzba · Answer 2 · 2016-07-19T19:35:58.267

The following function return the integer value or None in case the string is not valid integer:

def parseInt(ss):
    try:
        return int(ss)
    except:
        return None

Use this function to check if the string is an integer:

for mid in file:
    qty = mid[38:53]
    qty = qty.lstrip("0")
    qty = parseInt(qty)

    price = mid[75:86]
    price = price.lstrip("0")
    price = parseInt(price)

    if qty != None and price != None:
        value = qty*price
        trades = [qty,price,value]
        print (trades)
file.close()

Python using int function

2 Answers2