Programming Forums > Script Programming > Python

357mag · Jul 6th, 2007, 10:42 PM

I've written this program both in Java and in C++, so now I'm trying to do it in Python. All the program does is use a loop from 1 to 5 and output each number followed by that number squared. It outputs the numbers in columns, so it needs to look like this:

(Toggle Plain Text)

Value     Square
   1            1
   2            4
   3            9
   4            16
   5            25

Here is all I got so far:

(Toggle Plain Text)

def square(x):
    return x * x
    

print "Value   Square"


for i in range(1, 6):
    print i + "   " + square(i)

But of course it's wrong cuz the compiler tells me I can't concatanate and integer with " ". I'm looking for some way to tell the compiler to first print the value of i then move over to the next column, and print that value squared. Then after that, move to the next line and do the same for the next value of i.

Wizard1988 · Jul 6th, 2007, 11:10 PM

I don't usually play with python but here is something you can try.

(Toggle Plain Text)

def square(x):
    return x * x

print "Value\tSquare"

for i in range(1,6):
    print '%1d \t\t %2d' % (i, square(i))

Or:

(Toggle Plain Text)

print "Value\tSquare"

for i in range(1,6):
    print '%1d\t\t%2d' % (i,i*i)

Yet better:

(Toggle Plain Text)

print "Value\tSquare"

for i in range(1,6):
    print '%5d %8d' % (i,i*i)

You might want to read this about formatting strings

DaWei · Jul 6th, 2007, 11:23 PM

The problem with tabs, as you might or might not have discovered in your other thread, is that they represent "tab stops". If you're not familiar with typewriters, this might mean nothing. In many, many implementations they are considered to be set at multiples of 8. People come along and dink with that number all the time.

This is fine if every number you are ever going to output is smaller than the unknown size you have to deal with. Otherwise, you've been effed without being kissed.

If you want control over the appearance of your output, you need to look to the output formatting provisions of each language you fart with. Programmers have been dealing with this since they were in diapers. Some numbers need a space for a sign, even if it's blank. Some need trailing space for possible exponential notation. Some need to be right-justified. Some need to be left justified. Some need to be aligned on the decimal point, regardless of the length to either side.

The writers of the languages considered this, but they failed to imbue the language with enough magic to read your mind. You're supposed to be the one in control. Not every language is well documented, but you at least should look before you leap.

357mag · Jul 6th, 2007, 11:52 PM

I adjusted the numbers a bit:

(Toggle Plain Text)

print '%3d  %7d' % (i, square(i))

The numbers 3 and 7 that follow the percentage sign I believe mean to tell the compiler to right justify the number in a field width of 3 character postions, and the next number would be right justified in a field width of 7 character positions. But when I count the number of character positions from the first number to where the second number(under the Square column)is located, no way is that just 7. It's gotta be more than that.

DaWei · Jul 6th, 2007, 11:55 PM

Spaces that you put in the format string are put directly onto the output. Again, I'd recommend you consult the documentation. That can be confusing when you're trying to learn three languages in three days, I'll admit.

357mag · Jul 7th, 2007, 12:40 AM

Another question. The percentage sign. My understanding is that the percentage sign is just a placeholder for a value. So the first value of i would go into the %3d position, and the squared value of i would go into the %7d position. But what is the last percentage sign doing? The percentage sign right before the (i, square(i)) part?

Wizard1988 · Jul 7th, 2007, 1:01 AM

I think it just signifies that you will be listing variables next.

DaWei · Jul 7th, 2007, 9:40 AM

The quoted material below is from here.

Quote:

The % operator interprets the left argument much like a sprintf()-style format string to be applied to the right argument, and returns the string resulting from this formatting operation.

Quote:

(Toggle Plain Text)

>>> for x in range(1,11):
...     print '%2d %3d %4d' % (x, x*x, x*x*x)
... 
 1   1    1
 2   4    8
 3   9   27
 4  16   64
 5  25  125
 6  36  216
 7  49  343
 8  64  512
 9  81  729
10 100 1000

(Note that one space between each column was added by the way print works: it always adds spaces between its arguments.)

Dietrich · Jul 10th, 2007, 2:12 PM

Quote:

(Note that one space between each column was added by the way print works: it always adds spaces between its arguments.)

Whoever wrote that is full of dung, as it pertains to formatted strings. The space that you have in this example is the one from the format string.

Look at this:

(Toggle Plain Text)

for i in range(1, 6):
    print "%d-->%d" % (i, i*i)
"""
result (no spaces) ...
1-->1
2-->4
3-->9
4-->16
5-->25
"""

DaWei · Jul 10th, 2007, 2:15 PM

There's a link in the post; perhaps you should inform them

.

Jul 6th, 2007, 10:42 PM	#1
357mag Hobbyist Programmer Join Date: Mar 2005 Posts: 148 Rep Power: 4	How would I do this in Python? I've written this program both in Java and in C++, so now I'm trying to do it in Python. All the program does is use a loop from 1 to 5 and output each number followed by that number squared. It outputs the numbers in columns, so it needs to look like this: (Toggle Plain Text) Value Square 1 1 2 4 3 9 4 16 5 25 Value Square 1 1 2 4 3 9 4 16 5 25 Here is all I got so far: (Toggle Plain Text) def square(x): return x * x print "Value Square" for i in range(1, 6): print i + " " + square(i) def square(x): return x * x print "Value Square" for i in range(1, 6): print i + " " + square(i) But of course it's wrong cuz the compiler tells me I can't concatanate and integer with " ". I'm looking for some way to tell the compiler to first print the value of i then move over to the next column, and print that value squared. Then after that, move to the next line and do the same for the next value of i. Last edited by 357mag; Jul 6th, 2007 at 10:43 PM. Reason: mistake

Jul 6th, 2007, 11:10 PM	#2
Wizard1988 Professional Programmer Join Date: Oct 2005 Location: Chitown Posts: 422 Rep Power: 4	I don't usually play with python but here is something you can try. (Toggle Plain Text) def square(x): return x * x print "Value\tSquare" for i in range(1,6): print '%1d \t\t %2d' % (i, square(i)) def square(x): return x * x print "Value\tSquare" for i in range(1,6): print '%1d \t\t %2d' % (i, square(i)) Or: (Toggle Plain Text) print "Value\tSquare" for i in range(1,6): print '%1d\t\t%2d' % (i,ii) print "Value\tSquare" for i in range(1,6): print '%1d\t\t%2d' % (i,ii) Yet better: (Toggle Plain Text) print "Value\tSquare" for i in range(1,6): print '%5d %8d' % (i,ii) print "Value\tSquare" for i in range(1,6): print '%5d %8d' % (i,ii) You might want to read this about formatting strings __________________ Last edited by Wizard1988; Jul 6th, 2007 at 11:33 PM.

Jul 6th, 2007, 11:23 PM	#3
DaWei Resident Grouch Join Date: Jun 2005 Posts: 6,453 Rep Power: 10	The problem with tabs, as you might or might not have discovered in your other thread, is that they represent "tab stops". If you're not familiar with typewriters, this might mean nothing. In many, many implementations they are considered to be set at multiples of 8. People come along and dink with that number all the time. This is fine if every number you are ever going to output is smaller than the unknown size you have to deal with. Otherwise, you've been effed without being kissed. If you want control over the appearance of your output, you need to look to the output formatting provisions of each language you fart with. Programmers have been dealing with this since they were in diapers. Some numbers need a space for a sign, even if it's blank. Some need trailing space for possible exponential notation. Some need to be right-justified. Some need to be left justified. Some need to be aligned on the decimal point, regardless of the length to either side. The writers of the languages considered this, but they failed to imbue the language with enough magic to read your mind. You're supposed to be the one in control. Not every language is well documented, but you at least should look before you leap. __________________ Abstraction doesn't make it impossible to write bad code; it makes it possible to write superior code. Contributor's Corner: Grumpy on C++ Exceptions DaWei on Pointers

Jul 6th, 2007, 11:52 PM	#4
357mag Hobbyist Programmer Join Date: Mar 2005 Posts: 148 Rep Power: 4	I adjusted the numbers a bit: (Toggle Plain Text) print '%3d %7d' % (i, square(i)) print '%3d %7d' % (i, square(i)) The numbers 3 and 7 that follow the percentage sign I believe mean to tell the compiler to right justify the number in a field width of 3 character postions, and the next number would be right justified in a field width of 7 character positions. But when I count the number of character positions from the first number to where the second number(under the Square column)is located, no way is that just 7. It's gotta be more than that.

Jul 6th, 2007, 11:55 PM	#5
DaWei Resident Grouch Join Date: Jun 2005 Posts: 6,453 Rep Power: 10	Spaces that you put in the format string are put directly onto the output. Again, I'd recommend you consult the documentation. That can be confusing when you're trying to learn three languages in three days, I'll admit. __________________ Abstraction doesn't make it impossible to write bad code; it makes it possible to write superior code. Contributor's Corner: Grumpy on C++ Exceptions DaWei on Pointers

Jul 7th, 2007, 12:40 AM	#6
357mag Hobbyist Programmer Join Date: Mar 2005 Posts: 148 Rep Power: 4	Another question. The percentage sign. My understanding is that the percentage sign is just a placeholder for a value. So the first value of i would go into the %3d position, and the squared value of i would go into the %7d position. But what is the last percentage sign doing? The percentage sign right before the (i, square(i)) part?

Jul 7th, 2007, 1:01 AM	#7
Wizard1988 Professional Programmer Join Date: Oct 2005 Location: Chitown Posts: 422 Rep Power: 4	I think it just signifies that you will be listing variables next. __________________

Jul 10th, 2007, 2:15 PM	#10
DaWei Resident Grouch Join Date: Jun 2005 Posts: 6,453 Rep Power: 10	There's a link in the post; perhaps you should inform them . __________________ Abstraction doesn't make it impossible to write bad code; it makes it possible to write superior code. Contributor's Corner: Grumpy on C++ Exceptions DaWei on Pointers

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Programming Forums > Script Programming > Python

How would I do this in Python?