python - Can someone explain why replace isn't working for me -

i need remove spaces in sentences. sentence "i  like   python" , need make "i python". used replace this:

>>> >>> sentence="i    python" >>> def checkio(element):         newelement=element.replace("  ", " ") , element.replace("   ", " ")         return newelement  >>> checkio(sentence) 'i  python' >>> 

and see, result "i  like python" though (think) told replace "  " " ". can clear me why didn't work?

this wanted do:

def checkio(element):     newelement = element.replace("  ", " ").replace("   ", " ")     return newelement 

you shorten

def checkio(element):     return element.replace("  ", " ").replace("   ", " ") 

however, if wanted replace arbitrary number of spaces? better split sentence on number of spaces, , join single space. this, use

def checkio(element):     return " ".join(element.split()) 

the split method takes string , separates list. no argument, separates on spaces:

>>> "i     python".split() ["i", "like", "python"] 

the join method takes list , makes string out of it, using string in between elements of list:

>>> ' '.join(["i", "like", "python"]) "i python" >>> '__help__'.join(["i", "like", "python"]) "i__help__like__help__python" 

why original attempt failed

the line

newelement = element.replace("  ", " ") , element.replace("   ", " ") 

was not doing expect because using "truthiness" of strings. and operator looks @ logical things. in python, strings except "" considered true. can use called "short-circuiting", did.

when use and, both left , right statement must true evaluate true. if left part false, there no reason move on right part , evaluation stops there (aka "short-circuiting"). if true, needs check right side see if whole statement true. can exploit fact return left statement if false, or right if left true:

>>> = "a" , "b" >>> "b" >>> = "" , "b" >>> "" >>> # works oppositely "or" >>> = "a" or "b" >>> "a" >>> = "" or "b" >>> "b" 

element.replace(" ", " ") returns string, , element.replace(" ", " "). since strings evaluate true, ever returning right statement of and.

this not common use of logical operatiors in python (it more used in other languages, though)