Python check if line is empty or whitespace

Question

Check if String contains only Spaces #

To check if a string contains only spaces, call the trim() method on the string and check if the length of the result is equal to 0. If the string has a length of 0 after calling the trim method, then the string contains only spaces.

Table of Contents Show

Check if String contains only Spaces #
Check if String contains only with Regular Expression #
Further Reading #
How do I check if a string is empty or only spaces in Python?
How do you check if a line is blank in Python?
How do I check if a string contains whitespace?
How do you handle blank space in Python?

Copied!
function onlySpaces(str) {
  return str.trim().length === 0;
}

console.log(onlySpaces('   ')); // 👉️ true
console.log(onlySpaces('  123  ')); // 👉️ false
console.log(onlySpaces('hello ')); // 👉️ false
console.log(onlySpaces('')); // 👉️ true

The String.trim method removes the whitespace characters from both ends of a string.

We check if the result of calling the method on the string returns a string of length 0. If it does, we either have a string that contains only spaces or an empty string.

The trim method does not change the original string, it returns a new string. Strings are immutable in JavaScript.

An alternative, but also very common approach is to use a regular expression.

Check if String contains only with Regular Expression #

To check if a string contains only spaces, use the test() method with the following regular expression /^\s*$/. The test method will return true if the string contains only spaces and false otherwise.

Copied!
function onlySpaces(str) {
  return /^\s*$/.test(str);
}

console.log(onlySpaces('  ')); // 👉️ true
console.log(onlySpaces(' test ')); // 👉️ false
console.log(onlySpaces('hello ')); // 👉️ false
console.log(onlySpaces('')); // 👉️ true

We used the RegExp.test method to check if a string contains only spaces.

The method returns true if the regular expression is matched in the string and false otherwise.

The forward slashes / / mark the beginning and end of the regular expression.

The caret ^ matches the beginning of the input and the dollar sign $ matches the end of the input.

The \s character matches a single space, tab or newline.

The asterisk * character matches the preceding item (space) 0 or more times.

If you ever need help reading a regular expression, bookmark this regex cheatsheet from MDN.

Which approach you pick is a matter of personal preference. I'd go with the trim() method as I find it easier to read and more beginner friendly.

example

print('Hello world'.isspace())
print('         '.isspace())

Output

False
True

You can also use regexes for the same result. For matching only whitespace, we can call the re.match(regex, string) using the regex metacharacter \s as follows: "^\s*$".

example

import re
print(bool(re.match('^\s+$', '  abc')))
print(bool(re.match('^\s+$', '          ')))

Output

False
True

Manogna

Updated on 13-Feb-2020 09:59:53

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How do I check if a string is empty or only spaces in Python?

Python String isspace() method returns “True” if all characters in the string are whitespace characters, Otherwise, It returns “False”. This function is used to check if the argument contains all whitespace characters, such as: ' ' – Space.

How do you check if a line is blank in Python?

Use an if-statement to check if a line is empty Call file. readlines() to return all lines in file . Use a for-loop to iterate through each line. For each line, use an if-statement with the syntax if line == "\n" to check if line contains only a newline character.

How do I check if a string contains whitespace?

Approach:.

Get the String to be checked in str..

We can use the trim() method of String class to remove the leading whitespaces in the string. ... .

Then we can use the isEmpty() method of String class to check if the resultant string is empty or not. ... .

Combine the use of both methods using Method Chaining..

How do you handle blank space in Python?

strip() Python String strip() function will remove leading and trailing whitespaces. If you want to remove only leading or trailing spaces, use lstrip() or rstrip() function instead.

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