在Mac OS X上的终端中使用已安装的3.4版本运行Python脚本

Question

Python comes preinstalled on Macs with version 2.7, but I installed python 3.4. Let's say I make a simple program...

a = 1
b = 2 

print('\nVariable a Is :' , 'One' if (a==1) else 'Not One')
print('Variable a is : ' , 'Even' if (a % 2==0) else 'Odd')

print('\nVariable b is:' , 'One' if(b == 1) else 'Not One')
print('Variable b is', 'Even' if(b % 2 ==0) else 'Odd')

max = a if(a > b) else b

print( '\nGreater Value Is:', max)

If I make this program in TextWrangler, and then run it in terminal, the \\n escape sequence will still show up when it really isn't supposed to. Does this have to do with the version number I am running the script with, if so how can I change to using Python 3.4?

The program is from the book - Python in easy steps

Answer 1

If you run your file with python yourfile.py it will run with Python 2.7. Unless you did something unusual when installing Python 3.4, you need to use python3 yourfile.py to get that version.

Answer 2

The reason \\n shows up in your output is because you're using the , within the print statement, which will create a tuple of the two objects you passed in. In the string representation, the \\n does not get parsed, but simply shown.

Means:

>>> print( '\nGreater Value Is:', 1)
('\nGreater Value Is:', 1)

As you see, it created ('\\nGreater Value Is:', 1) .

To avoid this, use .format() or the % -style syntax:

>>> print('Greater value is: {0}'.format(23))
Greater value is: 23

Btw. don't use max as a variable name, since it's a built-in function in Python.