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Python Tips and Tricks

Here are a few handy tips and tricks, for those who are fairly new to Python.

while True:

Generally you'll come across many situations which involve variable assignment, followed by a while loop which performs any number of operations on this variable. For example:

You want to generate random numbers between 1 and 10, and stop when this number is odd, printing the number you get.

myvar = random.randint(1, 10)
while not (myvar % 2) == 1:
..myvar = random.randint(1, 10)
print myvar

This isn't very maintainable code - what if you later decided the range should be 1-100? You would have to edit two sections of your code.

Since Python doesn't support variable assignment within conditional statements, which some would argue is the most elegant solution, the most appropriate method to use here is as follows:

while True:
..myvar = random.randint(1, 10)
..if (myvar % 2) == 1: break
print myvar

Conditions

When writing conditions, I often see people trying to write:

if myvar == 0:
..

and

if bool(myvar) == True:
..

This is entirely unnecessary. Python takes most datatypes as either true or false to begin with, so it's actually much simpler - and easier to follow - to just use:

if myvar:
..

What counts as False?

• Integer 0
• Empty Strings
• Empty Lists/Tuples
• None

Single line conditions

When you've only got one line of code to execute after a condition, it's often faster to type it directly after the colon, rather than using a new line and indenting:

if myvar == 5: print 'hello world!'

Obviously, whether you consider this more or less readable is up to you. Hint - this also works perfectly for defining functions.

Ternary Operation

You might be familiar with seeing these written as follows:
condition ? value-if-true : value-if-false

Many people like to use dictionaries or and/or to simulate ternary operators in Python, but neither of these methods is completely safe from error. Far better to use the built in method:

value-if-true if-condition else value if-false

For example:

'Pi equals 3.15' if math.pi == 3.14 else '3.14 ain't approximate enough'

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