CODEWITHSUNDEEP
pythonsyntax
Bran.Ram
Bran.Ram

Reputation: 21

syntax error i've never seen before

i'm writing a phylogenetic tree program in python and i'm running into a small problem i've not encountered before, i have looked into it and nothing quite describes the problem i have, i get a syntax error from this code:

 for x in range(len(matrix)):
            # Print the label
            print(seq0[x-1], end == ' ') if x > 0 else print( ' ', end == '')

the error says:

 File "/home/brandon/OptimalAlignmentSensitive.py", line 206
print(seq0[x-1], end == ' ') if x > 0 else print( ' ', end == '')

and it points to the 't' in the second print statement. has anyone else had this problem? i don't understand what to do i have tried adding spaces and such but nothing helps.

Upvotes: 2

Views: 153

Answers (2)

Gareth Latty
Gareth Latty

Reputation: 88977

Your issue is the use of the ternary operator. You are using 2.x, where print is a statement - while the ternary operator only accepts expressions. Replace it with an if statement:

 for x in xrange(len(matrix)):
     if x > 0:
         print(seq0[x-1], end == ' ')
     else:
         print(' ', end == '')

This probably won't do what you want though. This will print a tuple, while you probably wanted to use the keyword argument from 3.x's print() function. This doesn't exist in 2.x, and instead, that functionality is produced by leaving a trailing comma (without brackets to construct a tuple).

 for x in range(len(matrix)):
     if x > 0:
         print seq0[x-1], 
     else:
         print " ",

In general, using the ternary operator to emulate a single line if statement is a bad practice anyway, even where it does work. As stated in my comments, iteration by index is generally a bad idea, and can probably be removed, but that would require more insight into the operation at hand.

Upvotes: 1

aldeb
aldeb

Reputation: 6828

Try adding from __future__ import print_function, and writing print(' ', end='') with a single '=' in the print function.

Upvotes: 4

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