[python] Check if string contains only whitespace

How can I test if a string contains only whitespace?

Example strings:

• " " (space, space, space)

• " \t \n " (space, tab, space, newline, space)

• "\n\n\n\t\n" (newline, newline, newline, tab, newline)

I'm assuming in your scenario, an empty string is a string that is truly empty or one that contains all white space.

if(str.strip()):
    print("string is not empty")
else:
    print("string is empty")

Note this does not check for None

You can use the str.isspace() method.

I used following:

if str and not str.isspace():
  print('not null and not empty nor whitespace')
else:
  print('null or empty or whitespace')

str.isspace() returns False for a valid and empty string

>>> tests = ['foo', ' ', '\r\n\t', '']
>>> print([s.isspace() for s in tests])
[False, True, True, False]

Therefore, checking with not will also evaluate None Type and '' or "" (empty string)

>>> tests = ['foo', ' ', '\r\n\t', '', None, ""]
>>> print ([not s or s.isspace() for s in tests])
[False, True, True, True, True, True]

Here is an answer that should work in all cases:

def is_empty(s):
    "Check whether a string is empty"
    return not s or not s.strip()

If the variable is None, it will stop at not sand not evaluate further (since not None == True). Apparently, the strip()method takes care of the usual cases of tab, newline, etc.

Resemblence with c# string static method isNullOrWhiteSpace.

def isNullOrWhiteSpace(str):
  """Indicates whether the specified string is null or empty string.
     Returns: True if the str parameter is null, an empty string ("") or contains 
     whitespace. Returns false otherwise."""
  if (str is None) or (str == "") or (str.isspace()):
    return True
  return False

isNullOrWhiteSpace(None) -> True // None equals null in c#, java, php
isNullOrWhiteSpace("")   -> True
isNullOrWhiteSpace(" ")  -> True

Check the length of the list given by of split() method.

if len(your_string.split()==0:
     print("yes")

Or Compare output of strip() method with null.

if your_string.strip() == '':
     print("yes")

To check if a string is just a spaces or newline

Use this simple code

mystr = "      \n  \r  \t   "
if not mystr.strip(): # The String Is Only Spaces!
    print("\n[!] Invalid String !!!")
    exit(1)
mystr = mystr.strip()
print("\n[*] Your String Is: "+mystr)

for those who expect a behaviour like the apache StringUtils.isBlank or Guava Strings.isNullOrEmpty :

if mystring and mystring.strip():
    print "not blank string"
else:
    print "blank string"

You want to use the isspace() method

str.isspace()

Return true if there are only whitespace characters in the string and there is at least one character, false otherwise.

That's defined on every string object. Here it is an usage example for your specific use case:

if aStr and (not aStr.isspace()):
    print aStr