How to check whether user entered the string in raw_input or not (in python)?

Question

My script asks for user interaction and asks for his/her name. I am using raw_input to exhibit this functionality. I want to check whether user gave any input or not. I thought to check the entered string with a blank. Currently the code looks like this :

str = raw_input("Enter your name: ")
if("" in str):
    print "user din't entered anything"

The above code works partially and if user presses enter without any input, the output user din't entered anything is printed.

The issue is that the above code also works when user enters something like foo bar [Notice the space between foo and bar. Yes I know why this is happening.

Another alternative is to check the length of string entered. If user does not enter anything then length would be zero. But same issue arises here. What if user enters more than one blank ! The length logic will fail.

What shall I do to check whether user inputted any string or left it blank ? Is there anything for string in python where I can do if(str == "") Any help appreciated.

Thanks for the quick reply but this fails with more than one blank. — node_analyser
– node_analyser, Commented Jul 2, 2014 at 7:44
@v1h5: Why do you say "more than one blank"? Assuming by "blank" you mean whitespace characters, it treats any amount of whitespace as valid input, not just more than one. Also, '' in x is true for any string x, not just for strings with spaces in them. — user2357112
– user2357112, Commented Jul 2, 2014 at 7:51
My bad. I just din't realize that in solving the matter :). +1 for bringing that to notice. Thanks. — node_analyser
– node_analyser, Commented Jul 2, 2014 at 8:02

sundar nataraj · Accepted Answer · 2014-07-02 07:53:13Z

2

value = raw_input("Enter your name: ")
if not value.strip():
    print "user din't entered anything"

strip() removes the trailling blank spaces and between word . if it is empty spaces . it remove all

edited Jul 2, 2014 at 7:53

answered Jul 2, 2014 at 7:44

sundar nataraj

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4 Comments

Mattias Backman Over a year ago

I think that comment from @v1h5 was written before the logic was fixed.

user2357112 Over a year ago

"and between word" - no it doesn't. It removes leading and trailing whitespace, but not between words.

node_analyser Over a year ago

I entered <blank>foo<blank><bar><blank><blank> and the output says "User din't entered anything" .. :-/

sundar nataraj Over a year ago

@v1h5 please try with updated one.i tried same i am not getting it

John La Rooy · Accepted Answer · 2014-07-02 07:46:35Z

1

isspace() checks if the string is just spaces without needing to create a new string object as strip() would

if(not str or str.isspace()):
    print "user din't entered anything"

Aside: str is a builtin. Shadowing it with your own variables can cause interesting bugs

answered Jul 2, 2014 at 7:46

John La Rooy

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3 Comments

John La Rooy Over a year ago

@user2357112, indeed. That case needs to be checked for

node_analyser Over a year ago

This is working perfectly fine. I am accepting this as answer. cheers @gnibbler

node_analyser Over a year ago

and yes, str is a function in python. I used str just for the sake of example. I will take care not to use this. :)

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