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

• Difficulty Level : Easy
• 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

1. Insert the given string in a set
2. 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

1. Iterate for every character and check if the character is 0 or 1.
2. If it is not then set a counter and break.
3. 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

1. Compile a regular expression using compile() for “character is not 0 or 1”.
2. Use re.findall() to fetch the strings satisfying the above regular expression.
3. 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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