If i in list

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March 18th, 2013, 03:25 PM

ishaan

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If i in list

I am trying to check whether the input matches either of the fruits in the list or '1'
It works (prints "Correct!" and exits) if I type in '1' and press enter. However, when I type in 'apples' (for example, or any other fruit) it doesn't work and the loop repeats asking "Enter a fruit:".
It obviously works when i replace

Code:

if fru in [fruits, '1']

with

Code:

 if fru in fruits or fru=='1'

But that's not how I want to write the code. I want the code to be as short as possible

Here is my code -

Code:

from sys import exit
fruits = ['apples','oranges','bananas','mangos','strawberries']

def checkfruit():
	fru = raw_input("Enter a fruit: ")
	if fru in [fruits, '1']:
		print "Correct!"
		exit(0)
	else:
		checkfruit()

		
checkfruit()

Any help would be appreciated! I couldn't find "in" anywhere in Python docs, or maybe I didn't check them correctly. Just started with python yesterday hehe.

March 18th, 2013, 04:22 PM

codergeek42

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The first thing that comes to mind is to make them both sets and then check if '1' is in their union:

python Code:

Original - python Code
if fru in set(fruits) \| set(['1']): print("Correct!")

if fru in set(fruits) | set(['1']):
    print("Correct!")

Alternatively, you could flatten the [fruits, '1'] list by calling into the compiler.ast module, and use that:

python Code:

Original - python Code
from compiler.ast import flatten # ... if fru in flatten([fruits, '1']): print("Correct!")

from compiler.ast import flatten
 
# ...
 
if fru in flatten([fruits, '1']):
    print("Correct!")

To be quite frank though, I feel that your original if statement is the ideal one:

python Code:

Original - python Code
if fru in fruits or fru=='1': print("Correct!")

if fru in fruits or fru=='1':
    print("Correct!")

Keep in mind The Zen of Python, particularly "Explicit is better than implicit" and "Readability counts". In your original if statement, it's very clear to see what the conditions are; whereas in the other two, even if it does the check against only one list (or set), it takes a bit more thought to see what the conditions are and when it would be true/false.

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March 19th, 2013, 02:59 AM

SuperOscar

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Quote:

Originally Posted by codergeek42

The first thing that comes to mind is to make them both sets and then check if '1' is in their union:

Well sure, but it’s just as easy to use list concatenation:

Code:

if fru in fruits + ['1']:

Quote:

Alternatively, you could flatten the [fruits, '1'] list by calling into the compiler.ast module, and use that:

I have no idea where you got that compiler.ast thingy–seems not be present in my Python installations, nor is it documented in docs.python.org!

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