Python 实用宝典

Question 1

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)

Question 2

Use the str.isspace() method:

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

A character is whitespace if in the Unicode character database (see unicodedata), either its general category is Zs (“Separator, space”), or its bidirectional class is one of WS, B, or S.

Combine that with a special case for handling the empty string.

Alternatively, you could use str.strip() and check if the result is empty.

Question 3

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

Question 4

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

Question 5

You can use the str.isspace() method.

Question 6

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"

Question 7

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")

Question 8

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.

Question 9

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

Question 10

I used following:

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

Question 11

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)

Question 12

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

Python 实用宝典

如何在Python中检查文本是否为“空”（空格，制表符，换行符）？

问题：如何在Python中检查文本是否为“空”（空格，制表符，换行符）？

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