CODEWITHSUNDEEP
pythonpython-2.7
derkyzer
derkyzer

Reputation: 161

Conditional in the Middle of an Expression

I'm curious if something like this is possible:

print "lajsdflk"+ (if x>1:"123123";else:"0000000") +"!@#"

Not specifically printing but just any function with numbers; another example:

print 596* (if statementX: 6545; else: 9874) /63

If possible I'd like to keep it to one line.

Upvotes: 2

Views: 178

Answers (1)

thefourtheye
thefourtheye

Reputation: 239523

You can use conditional expression, like this

>>> "lajsdflk" + ("123123" if 5 > 1 else "0000000") + "!@#"
'lajsdflk123123!@#'
>>> "lajsdflk" + ("123123" if 0 > 1 else "0000000") + "!@#"
'lajsdflk0000000!@#'

Since Python accepts any Truthy value in the if's expression, you can even use any function, like this

>>> "lajsdflk" + ("123123" if "abcd1234".isalnum() else "0000000") + "!@#"
'lajsdflk123123!@#'

There is another trick people use. It goes like this

>>> "lajsdflk" + ("0000000", "123123")[5 > 1] + "!@#"
'lajsdflk123123!@#'
>>> "lajsdflk" + ("0000000", "123123")[0 > 1] + "!@#"
'lajsdflk0000000!@#'

Here, a tuple is prepared with the possible outcomes and based on the result of the comparison operation, the possible value is chosen. Here, 5 > 1 is evaluated and found out to be Truthy and since Python's True equals 1 and False equals 0, 5 > 1 evaluates to be 1.

>>> 0 == False
True
>>> 1 == True
True

Note: This trick has a problem. Consider this case,

>>> 1 + (2, 3/0)[4 > 0] + 5
Traceback (most recent call last):
  File "<input>", line 1, in <module>
ZeroDivisionError: integer division or modulo by zero

Because, when the tuple is created all the values are evaluated and Python cannot divide 1 by 0. But, this problem will not be there with conditional expression,

>>> 1 + (2 if 4 > 0 else 3/0) + 5
8

Because it evaluates the values only if the branch is hit.

Upvotes: 5

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