Python | Check if a given string is binary string or not

Difficulty Level : Basic
Last Updated : 25 Aug, 2021

Given a string str. The task is to check whether it is a binary string or not.
Examples:

Input: str = "01010101010"
Output: Yes

Input: str = "geeks101"
Output: No

Approach 1: Using Set

Insert the given string in a set
Check if the set characters consist of 1 and/or 0 only.

Python3

# Python program to check
# if a string is binary or not
 
# function for checking the
# string is accepted or not
def check(string) :
 
    # set function convert string
    # into set of characters .
    p = set(string)
 
    # declare set of '0', '1' .
    s = {'0', '1'}
 
    # check set p is same as set s
    # or set p contains only '0'
    # or set p contains only '1'
    # or not, if any one condition
    # is true then string is accepted
    # otherwise not .
    if s == p or p == {'0'} or p == {'1'}:
        print("Yes")
    else :
        print("No")
 
 
         
# driver code
if __name__ == "__main__" :
 
    string = "101010000111"
 
    # function calling
    check(string)

Output

Yes

Approach 2: Simple Iteration

Iterate for every character and check if the character is 0 or 1.
If it is not then set a counter and break.
After iteration check whether the counter is set or not.

Python3

# Python program to check
# if a string is binary or not
 
# function for checking the
# string is accepted or not
def check2(string) :
 
    # initialize the variable t
    # with '01' string
    t = '01'
 
    # initialize the variable count
    # with 0 value
    count = 0
 
    # looping through each character
    # of the string .
    for char in string :
 
        # check the character is present in
        # string t or not.
        # if this condition is true
        # assign 1 to the count variable
        # and break out of the for loop
        # otherwise pass
        if char not in t :
            count = 1
            break
        else :
            pass
         
    # after coming out of the loop
    # check value of count is non-zero or not
    # if the value is non-zero the en condition is true
    # and string is not accepted
    # otherwise string is accepted
    if count :
        print("No")
    else :
        print("Yes")
 
 
 
# driver code
if __name__ == "__main__" :
 
    string = "001021010001010"
 
    # function calling
    check2(string)

Output

No

Approach 3: Regular Expressions

Compile a regular expression using compile() for “character is not 0 or 1”.
Use re.findall() to fetch the strings satisfying the above regular expression.
Print output based on the result.

Python3

#import library
import re
 
sampleInput = "1001010"
 
# regular expression to find the strings
# which have characters other than 0 and 1
c = re.compile('[^01]')
 
# use findall() to get the list of strings
# that have characters other than 0 and 1.
if(len(c.findall(sampleInput))):
    print("No") # if length of list > 0 then it is not binary
else:
    print("Yes") # if length of list = 0 then it is binary

Output

Yes

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