How do you check if a field is empty in python?

While s = "" ? How to check if the input I receive is empty using only the while command.

You can check input is empty or not with the help of if statement. x=input() if x: print(x) else: print('empty input')

How do you check if a field is empty in python?

A tip: when you are dealing with EOF or something alike always remember that, to python, every null or empty or zero it's managed like a "false"... So you can put something like "while s:" because, if it's null or empty, will be false to python

How do you check if a field is empty in python?

One pattern would be: s = input() while s: somelist.append(s) s = input() It's a bit annoying to write the same line twice, but there is no 'do while' like in c. Or you use this: while True: s = input() if not s: break somelist.append(s)

How do you check if a field is empty in python?

input() returns a string. To check whether it is empty, just check its length. s=input() while len(s)==0: s=input()

How do you check if a field is empty in python?

You might want to use the catch exception method. Whenever you enter an input, in case that input is empty, it produces an End of File Error written as EOFError. So your code should look something like this, try: #enter input s = input() #do something with your input except EOFError: #action when input is empty or there is no input The code above should do it. ;)

How do you check if a field is empty in python?

x=input() if not x: print('empty input')

How do you check if a field is empty in python?

I find hardcoding(sic) "" every time for checking an empty string not as good.

Clean code approach

Doing this: foo == "" is very bad practice. "" is a magical value. You should never check against magical values (more commonly known as magical numbers)

What you should do is compare to a descriptive variable name.

Descriptive variable names

One may think that "empty_string" is a descriptive variable name. It isn't.

Before you go and do empty_string = "" and think you have a great variable name to compare to. This is not what "descriptive variable name" means.

A good descriptive variable name is based on its context. You have to think about what the empty string is.

  • Where does it come from.
  • Why is it there.
  • Why do you need to check for it.

Simple form field example

You are building a form where a user can enter values. You want to check if the user wrote something or not.

A good variable name may be not_filled_in

This makes the code very readable

if formfields.name == not_filled_in:
    raise ValueError("We need your name")

Thorough CSV parsing example

You are parsing CSV files and want the empty string to be parsed as None

(Since CSV is entirely text based, it cannot represent None without using predefined keywords)

A good variable name may be CSV_NONE

This makes the code easy to change and adapt if you have a new CSV file that represents None with another string than ""

if csvfield == CSV_NONE:
    csvfield = None

There are no questions about if this piece of code is correct. It is pretty clear that it does what it should do.

Compare this to

if csvfield == EMPTY_STRING:
    csvfield = None

The first question here is, Why does the empty string deserve special treatment?

This would tell future coders that an empty string should always be considered as None.

This is because it mixes business logic (What CSV value should be None) with code implementation (What are we actually comparing to)

There needs to be a separation of concern between the two.

  • Introduction
  • 7 Different ways to check if the string is empty or not
    • 1. Using len() method
    • 2. Using not operator To Check If String Is Empty String In Python
    • 3. Using and operator + strip() function to check if string is empty string in python
    • 4. Using Strip() function only To Check Empty String In Python
    • 5. Using not operator + str.isspace()
    • 6. Using __eq__ method
    • 7. Using Regex To Check Empty String In Python
  • Conclusion

Introduction

Python strings are immutable, i.e., we can change the strings according to the operations performed. String Manipulation is the most important feature in python. You can manipulate the string by many methods such as String slicing techniques, looping over the elements, and string methods. But. Sometimes we come to the situation where we need to check if the Python string is empty or not and the list is empty. In this article, we will be discussing ways to check if the string is empty or not in Python.

NOTE : String which has spaces in them are empty string but has a non-zero size.

7 Different ways to check if the string is empty or not

Let us discuss certain ways through which we can check if the string is an empty string or not.

1. Using len() method

We will be calculating the length of the string with the help of len() in python. Then, we will check if the string’s length is equal to 0, then the string is empty; otherwise, not.

NOTE: If the string contains spaces in it the string is not treated as the empty string by using the len() function in python 

Let us look at the example for the better understanding of the concept:

#input empty with and without spaces string
s = ""
str = "    "

x = len(s)
y = len(str)

if x == 0:
    print("string is empty")
else:
    print("string is not empty")
    
if y == 0:
    print("string is empty")
else:
    print("string is not empty")

Output:

string is empty
string is not empty

Explanation:

Here, we have taken two input strings, s and str. s is an empty string, and str has whitespaces. Then, we have calculated the length of both the strings with the len() function in python. Then, we have applied the if-else loop and checked if the string’s length is equal to 0, then the print string is empty, and if it is not empty, print not empty. In the len(), whitespaces are not treated as empty in the string, giving the output as a not empty string. At last, we have printed the output of both the string.

2. Using not operator To Check If String Is Empty String In Python

Not operator is used to perform the same task as of len() function. The empty string is always equivalent to False in Python. If we want to check if the string is empty or not, we can check it with the help of not operator.

NOTE: If the string contains spaces in it the string is not treated as the empty string by using the not operator in python 

Let us look at the example for the better understanding of the concept:

#input empty with and without spaces string
s = ""
str = "    "

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

Output:

string is empty
string is not empty

Explanation:

Here, we have taken two input strings, s and str. s is an empty string, and str has whitespaces. Then, we have applied if else condition in which we have checked if not in string, then the string is empty. Otherwise, it is not empty. The not operator also does not treat whitespaces as the empty string so that the output will come as not an empty string of the second input string. At last, we have printed the output.

3. Using and operator + strip() function to check if string is empty string in python

Sometimes, we see that the whitespaces present in the string are not treated as empty strings. So, when we check for the empty string, we can also check for the whitespaces through the strip() function.

Let us look at the example for the better understanding of the concept:

#input empty with and without spaces string
s = ""
str = "    "

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

Output:

string is empty
string is empty

Explanation:

Here, we have taken two input strings, s and str. s is an empty string, and str has whitespaces. We have applied the if-else condition and checked with the strip() function that the string is empty or not. If the condition gets False, that means the string is empty, and else blocks get executed. In this function, whitespace is also treated as empty strings. At last, we have printed the output.

4. Using Strip() function only To Check Empty String In Python

Sometimes, we see that the whitespaces present in the string are not treated as empty strings. So, when we check for the empty string, we can also check for the whitespaces through the strip() function.

Let us look at the example for the better understanding of the concept:

#input empty with and without spaces string
s = ""
str = "    "

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

Output:

string is empty
string is empty

Explanation:

Here, we have taken two input strings, s and str. s is an empty string, and str has whitespaces. We have applied if else condition in which we strip the strings, i.e., whitespaces gets removed, and then if the string gets empty, it will be an empty string. Otherwise, the string is not empty. At last, we have printed the output.

5. Using not operator + str.isspace()

It works the same as the strip() function as it checks for the whitespaces in the strip. But, strip() function a lot of time as compared to str. isspace() function because strip() has to perform strip operation, which takes a lot of computation loads.

Let us look at the example for the better understanding of the concept:

#input empty with and without spaces string
s = ""
str = "    "

if s and not s.isspace():
    print("string is not empty")
else:
    print("string is empty")
    
if str and not str.isspace():
    print("string is not empty")
else:
    print("string is empty")

Output:

string is empty
string is empty

Explanation:

Here, we have taken two input strings, s and str. s is an empty string, and str has whitespaces. We have applied the if-else condition. In the if-else condition, we have applied the isspace() function, which will check all the string spaces. Finally, we have printed the output, and you can see the output that both the strings are empty.

6. Using __eq__ method

The dunder basically tells the methods that have double underscores before and after their names. We can check empty string through the __eq__ method also.

NOTE: If the string contains spaces in it the string is not treated as the empty string by using the __eq__ method in python 

Let us look at the example for the better understanding of the concept:

#input empty with and without spaces string
s = ""
str = "    "

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

Output:

string is empty
string is not empty

Explanation:

Here, we have taken two input strings, s and str. s is an empty string, and str has whitespaces. We have taken the __eq__ method. We have applied the given method in the if-else condition and checked if the string is empty or not. At last, we have printed the output. This method also doesn’t treat whitespaces as empty strings.

7. Using Regex To Check Empty String In Python

We can create a regex pattern to check if the given string is either empty or contains only white spaces.

Let us look at the example for the better understanding of the concept:

#import re library
import re
s = ""
str = "         "

if not s or re.search("^\s*$", s):
    print('String is empty or has spaces')
else:
    print('String is not empty')
if not s or re.search("^\s*$", s):
    print('String is empty or has spaces')
else:
    print('String is not empty')

Output:

String is empty or has spaces
String is empty or has spaces

Explanation:

Here, we have taken two input strings, s and str. s is an empty string, and str has whitespaces. We have imported the re library in python. Then, we have applied the if-else condition with the given format to check whether the string is empty or not. If the if-condition satisfies, then the output gets printed as it is an empty string. Otherwise, Output gets printed as not an empty string. Hence, you can see the output.

Also Read: 5 Ways to Check if a String is Integer in Python

Conclusion

In this tutorial, we have learned about the concept of checking the string is empty or not and if the string contains whitespaces only or not. We have explained the full concept in detail by taking all the ways to check if the string is empty. All the ways are explained in detail with the help of examples. You can use any of the methods you like to use according to your program or project requirement.

However, if you have any doubts or questions, do let me know in the comment section below. I will try to help you as soon as possible.

How do you check if a value is empty in Python?

Method #1 : Using len() Using len() is the most generic method to check for zero-length string. Even though it ignores the fact that a string with just spaces also should be practically considered as empty string even its non zero.

How do I check if a Python input box is empty?

You can use the isspace() and "" (empty string).

How do you check if a variable is an empty list?

Empty lists are considered False in Python, hence the bool() function would return False if the list was passed as an argument. Other methods you can use to check if a list is empty are placing it inside an if statement, using the len() methods, or comparing it with an empty list.

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