Programming Forums > Script Programming > Python

HaCkeR · Nov 29th, 2005, 10:57 AM

I just wrote this program and it's my first actual program with a use.I
want to know what you think please let me know and if i can improve
it i want to know how.

its a basic calculator

(Toggle Plain Text)

print "the legable symbols are '+','-','/' and '*'"
print "it on a 10 loop so you can use it 10 times"
print

loop = 0
while (loop < 10):
    loop = loop + 1
    def plus():
        print var_1, "+", var_3, "=", var_1 + var_3
    def min():
        print var_1, "-", var_3, "=", var_1 - var_3
    def multi():
        print var_1, "*", var_3, "=", var_1 * var_3
    def div():
        print var_1, "/", var_3, "=", (var_1 + 0.0) / var_3
    var_1 = input ("Type first number:")
    var_2 = raw_input ("Type Operation:")
    var_3 = input ("Type second number:")
    if var_2 == "+": plus()
    if var_2 == "-": min()
    if var_2 == "*": multi()
    if var_2 == "/": div()
    print

Dietrich · Nov 29th, 2005, 12:19 PM

Well, it's a good start. I would take the function defines out of the loop, so the interpreter has to do them only once. Then add an option to exit the while loop. Avoid the function input() and use raw_input() instead, it's much safer! Convert the string to a float to get your number. Another good thing is to add a "divide by zero error" trap. All things to learn!

(Toggle Plain Text)

# took def out of the loop and added quit option
# also switched to raw_input and convert to float
# added divide by zero trap

print "the legable symbols are '+','-','/' and '*'"
print "it on a 10 loop so you can use it 10 times"
print

def plus():
    print var_1, "+", var_3, "=", var_1 + var_3
def min():
    print var_1, "-", var_3, "=", var_1 - var_3
def multi():
    print var_1, "*", var_3, "=", var_1 * var_3
def div():
    if var_3 == 0:
        print "division by zero error"
    else:
        print var_1, "/", var_3, "=", (var_1 + 0.0) / var_3
        
loop = 0
while (loop < 10):
    loop = loop + 1
    try:
        var_1 = float(raw_input ("Type first number (q to quit):"))
        var_2 = raw_input ("Type Operation:")
        var_3 = float(raw_input ("Type second number:"))
    except:
        # entering q would be an error so it goes here:
        print "Thank you for using my calculator program!"
        break
    if var_2 == "+": plus()
    if var_2 == "-": min()
    if var_2 == "*": multi()
    if var_2 == "/": div()
    if var_2 == "q": break
    print

HaCkeR · Nov 29th, 2005, 12:29 PM

thanks for that but for some reason all your code does is restarts the shell.
i cannot think why because i looked at it and it seems fine

Arevos · Nov 29th, 2005, 12:45 PM

Another tip is to avoid global variables when they're not needed. Make your operator functions more general:

(Toggle Plain Text)

def add(a, b):
   return a + b

In fact, you don't even have to do this, since python provides the operator module:

(Toggle Plain Text)

import operator
two = operator.add(1, 1)   # same as 1 + 1

A dictionary could also be used in place of if statements. You could create a dictionary that associates an operator string (such as "+") with an operator function (such as operator.add):

(Toggle Plain Text)

from operator import add, sub, div, mul;
operator_map = { "+" : add, "-" : sub, "*" : mul, "/" : div }

You can then use operator_map to find the correct function and to execute it:

(Toggle Plain Text)

operator_map[val_2](val_1, val_3)

However, it might also be a good idea to name your variables something a little more descriptive than val_1 to val_3. Maybe: number_1, operator, number_2:

(Toggle Plain Text)

operator_map[operator](number_1, number_2)

HaCkeR · Nov 29th, 2005, 1:46 PM

Thanks for that. ive just started to learn C++ :p

Dietrich · Nov 30th, 2005, 2:32 PM

A very good idea to learn C++ and Python. Python's strength is readability and program development speed. It isn't too difficult to develop your program concepts in Python and then translate them to C++ or C for the compiled product. A very nice skill to develop!

The only thing that will drive you nuts, are the repetitious and dogmatic type declarations that come with C++. Python, being an interpreter, figures those out on the fly.

By the way, I happen to think that there are about 6 billion different types of people on this earth (presently).

Nov 29th, 2005, 10:57 AM	#1
HaCkeR Hobbyist Programmer Join Date: Nov 2005 Location: UK Posts: 131 Rep Power: 0	Opinion's wanted on some code I just wrote this program and it's my first actual program with a use.I want to know what you think please let me know and if i can improve it i want to know how. its a basic calculator (Toggle Plain Text) print "the legable symbols are '+','-','/' and ''" print "it on a 10 loop so you can use it 10 times" print loop = 0 while (loop < 10): loop = loop + 1 def plus(): print var_1, "+", var_3, "=", var_1 + var_3 def min(): print var_1, "-", var_3, "=", var_1 - var_3 def multi(): print var_1, "", var_3, "=", var_1 * var_3 def div(): print var_1, "/", var_3, "=", (var_1 + 0.0) / var_3 var_1 = input ("Type first number:") var_2 = raw_input ("Type Operation:") var_3 = input ("Type second number:") if var_2 == "+": plus() if var_2 == "-": min() if var_2 == "": multi() if var_2 == "/": div() print print "the legable symbols are '+','-','/' and ''" print "it on a 10 loop so you can use it 10 times" print loop = 0 while (loop < 10): loop = loop + 1 def plus(): print var_1, "+", var_3, "=", var_1 + var_3 def min(): print var_1, "-", var_3, "=", var_1 - var_3 def multi(): print var_1, "", var_3, "=", var_1 var_3 def div(): print var_1, "/", var_3, "=", (var_1 + 0.0) / var_3 var_1 = input ("Type first number:") var_2 = raw_input ("Type Operation:") var_3 = input ("Type second number:") if var_2 == "+": plus() if var_2 == "-": min() if var_2 == "*": multi() if var_2 == "/": div() print

Nov 29th, 2005, 12:19 PM	#2
Dietrich Professional Programmer Join Date: Feb 2005 Posts: 434 Rep Power: 4	Well, it's a good start. I would take the function defines out of the loop, so the interpreter has to do them only once. Then add an option to exit the while loop. Avoid the function input() and use raw_input() instead, it's much safer! Convert the string to a float to get your number. Another good thing is to add a "divide by zero error" trap. All things to learn! (Toggle Plain Text) # took def out of the loop and added quit option # also switched to raw_input and convert to float # added divide by zero trap print "the legable symbols are '+','-','/' and ''" print "it on a 10 loop so you can use it 10 times" print def plus(): print var_1, "+", var_3, "=", var_1 + var_3 def min(): print var_1, "-", var_3, "=", var_1 - var_3 def multi(): print var_1, "", var_3, "=", var_1 * var_3 def div(): if var_3 == 0: print "division by zero error" else: print var_1, "/", var_3, "=", (var_1 + 0.0) / var_3 loop = 0 while (loop < 10): loop = loop + 1 try: var_1 = float(raw_input ("Type first number (q to quit):")) var_2 = raw_input ("Type Operation:") var_3 = float(raw_input ("Type second number:")) except: # entering q would be an error so it goes here: print "Thank you for using my calculator program!" break if var_2 == "+": plus() if var_2 == "-": min() if var_2 == "": multi() if var_2 == "/": div() if var_2 == "q": break print # took def out of the loop and added quit option # also switched to raw_input and convert to float # added divide by zero trap print "the legable symbols are '+','-','/' and ''" print "it on a 10 loop so you can use it 10 times" print def plus(): print var_1, "+", var_3, "=", var_1 + var_3 def min(): print var_1, "-", var_3, "=", var_1 - var_3 def multi(): print var_1, "", var_3, "=", var_1 var_3 def div(): if var_3 == 0: print "division by zero error" else: print var_1, "/", var_3, "=", (var_1 + 0.0) / var_3 loop = 0 while (loop < 10): loop = loop + 1 try: var_1 = float(raw_input ("Type first number (q to quit):")) var_2 = raw_input ("Type Operation:") var_3 = float(raw_input ("Type second number:")) except: # entering q would be an error so it goes here: print "Thank you for using my calculator program!" break if var_2 == "+": plus() if var_2 == "-": min() if var_2 == "*": multi() if var_2 == "/": div() if var_2 == "q": break print __________________ I looked it up on the Intergnats!

Nov 29th, 2005, 12:45 PM	#4
Arevos Programming Guru Join Date: Aug 2005 Location: England Posts: 1,499 Rep Power: 5	Another tip is to avoid global variables when they're not needed. Make your operator functions more general: (Toggle Plain Text) def add(a, b): return a + b def add(a, b): return a + b In fact, you don't even have to do this, since python provides the operator module: (Toggle Plain Text) import operator two = operator.add(1, 1) # same as 1 + 1 import operator two = operator.add(1, 1) # same as 1 + 1 A dictionary could also be used in place of if statements. You could create a dictionary that associates an operator string (such as "+") with an operator function (such as operator.add): (Toggle Plain Text) from operator import add, sub, div, mul; operator_map = { "+" : add, "-" : sub, "" : mul, "/" : div } from operator import add, sub, div, mul; operator_map = { "+" : add, "-" : sub, "" : mul, "/" : div } You can then use operator_map to find the correct function and to execute it: (Toggle Plain Text) operator_map[val_2](val_1, val_3) operator_map[val_2](val_1, val_3) However, it might also be a good idea to name your variables something a little more descriptive than val_1 to val_3. Maybe: number_1, operator, number_2: (Toggle Plain Text) operator_map[operator](number_1, number_2) operator_map[operator](number_1, number_2)

Nov 30th, 2005, 2:32 PM	#6
Dietrich Professional Programmer Join Date: Feb 2005 Posts: 434 Rep Power: 4	A very good idea to learn C++ and Python. Python's strength is readability and program development speed. It isn't too difficult to develop your program concepts in Python and then translate them to C++ or C for the compiled product. A very nice skill to develop! The only thing that will drive you nuts, are the repetitious and dogmatic type declarations that come with C++. Python, being an interpreter, figures those out on the fly. By the way, I happen to think that there are about 6 billion different types of people on this earth (presently). __________________ I looked it up on the Intergnats!

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Nov 29th, 2005, 12:29 PM	#3
HaCkeR Hobbyist Programmer Join Date: Nov 2005 Location: UK Posts: 131 Rep Power: 0	thanks for that but for some reason all your code does is restarts the shell. i cannot think why because i looked at it and it seems fine

Nov 29th, 2005, 1:46 PM	#5
HaCkeR Hobbyist Programmer Join Date: Nov 2005 Location: UK Posts: 131 Rep Power: 0	Thanks for that. ive just started to learn C++ :p

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Programming Forums > Script Programming > Python

Opinion's wanted on some code