Remove Substring From String in Python
While handling text data in python, we sometimes need to remove a specific substring from the text. In this article, we will discuss different ways to remove a substring from a string in Python.
Remove Substring From String in Python Using split() Method
The split() method in Python is used to split a string into substrings at a separator. The split() method, when invoked on a string, takes a string in the form of a separator as its input argument. After execution, it returns a list of substrings from the original string, which is split at the separator.
To remove a substring from a string in Python using the split() method, we will use the following steps.
- First, we will create an empty string named output_string to store the output string.
- Then, we will use the split() method to split the string into substrings from the positions where we need to remove a specific substring. For this, we will invoke the split() method on the input string with the substring that needs to be removed as the input argument. After execution, the split() method will return a string of substrings. We will assign the list to a variable str_list .
- Once we get the list of strings, we will iterate through the substrings in str_list using a for loop. During iteration, we will add the current substring to output_string using the string concatenation operation.
After execution of the for loop, we will get the required output string in the variable output_string . You can observe this in the following code.
In the output, you can observe that the substring python has been removed from the input string.
Remove Substring From String in Python Using Using the join() Method
Performing string concatenation several times requires unnecessary storage and time. Therefore, we can avoid that by using the join() method.
The join() method, when invoked on a separator string, takes an iterable object as its input argument. After execution, it returns a string consisting of the elements of the iterable object separated by the separator string.
To remove substring from a string in python using the join() method, we will use the following steps.
- First, we will use the split() method to split the input string into substrings from the positions where we need to remove a specific substring. For this, we will invoke the split() method on the input string with the substring that needs to be removed as the input argument. After execution, the split() method will return a string of substrings. We will assign the list to a variable str_list .
- Next, we will invoke the join() method on an empty string with str_list as its input argument.
After execution of the join() method, we will get the required string output as shown below.
Here, you can observe that we have converted the list returned by the split() method into a string using the join() method. Thus, we have avoided repeated string concatenation as we did in the previous example.
Remove Substring From String in Python Using the replace() Method
The replace() method is used to replace one or more characters from a string in python. When invoked on a string, the replace() method takes two substrings as its input argument. After execution, it replaces the substring in the first argument with that of the second input argument. Then it returns the modified string.
To remove a substring from a string using the replace() method, we will invoke the replace() method on the original string with the substring that is to be removed as the first input argument and an empty string as the second input argument.
After execution of the replace() method, we will get the output string as shown in the following example.
Here, we have removed the required substring from the input string in a single statement using the replace() method.
Remove Substring From String in PythonUsing Regular Expressions
Regular expressions provide us with efficient ways to manipulate strings in Python. We can also use regular expressions to remove a substring from a string in python. For this, we can use the re.split() method and the re.sub() method.
Remove Substring From String in Python Using re.split() Method
The re.split() method is used to split a text at a specified separator. The re.split() method takes a separator string as its first input argument and the text string as its second input argument. After execution, it returns a list of strings from the original string that are separated by the separator.
To remove a substring from a string in Python using the re.split() method, we will use the following steps.
- First, we will create an empty string named output_string to store the output string.
- Then, we will use the re.split() method to split the string into substrings from the positions where we need to remove a specific substring. For this, we will execute the re.split() method with the substring that needs to be removed as its first input argument and the text string as its second input argument. After execution, the re.split() method will return a string of substrings. We will assign the list to a variable str_list .
- Once we get the list of strings, we will iterate through the substrings in str_list using a for loop. During iteration, we will add the current substring to output_string using the string concatenation operation.
After execution of the for loop, we will get the required output string in the variable output_string . You can observe this in the following code.
You can observe that the approach using the re.split() method is almost similar to the approach using the string split() method. However, both approaches have different execution speeds. If the input string is very large, the re.split() method should be the preferred choice to split the input string.
Performing string concatenation several times requires unnecessary memory and time. Therefore, we can avoid that by using the join() method.
To remove substring from a string in python using the join() method, we will use the following steps.
- First, we will use the re.split() method to split the input string into substrings from the positions where we need to remove a specific substring.For this, we will execute the re.split() method with the substring that has to be removed as its first input argument and the text string as its second input argument. After execution, the re.split() method will return a string of substrings. We will assign the list to a variable str_list .
- Next, we will invoke the join() method on an empty string with str_list as its input argument.
After execution of the join() method, we will get the required string output as shown below.
In this approach, we have obtained the output string in only two python statements. Also, we haven’t done repetitive string concatenation which takes unnecessary time.
Remove Substring From String in Python Using re.sub() Method
The re.sub() method is used to substitute one or more characters from a string in python. The re.sub() method takes three input arguments. The first input argument is the substring that needs to be substituted. The second input argument is the substitute substring. The original string is passed as the third input string.
After execution, the re.sub() method replaces the substring in the first argument with that of the second input argument. Then it returns the modified string.
To remove a substring from a string using the re.sub() method, we will execute the re.sub() method with the substring that is to be removed as the first input argument, an empty string as the second input argument, and the original string as the third input argument.
After execution of the re.sub() method, we will get the output string as shown in the following example.
The re.sub() method works in a similar manner to the replace() method. However, it is faster than the latter and should be the preferred choice.
Remove Substring From String in Python by Index
Sometimes, we might need to remove a substring from a string when we know its position in the string. To remove a substring from a string in python by index, we will use string slicing.
If we have to remove the substring from index i to j, we will make two slices of the string. The first slice will be from index 0 to i-1 and the second slice will be from index j+1 to the last character.
After obtaining the slices, we will concatenate the slices to obtain the output string as shown in the following example.
Conclusion
In this article, we have discussed different ways to remove a substring from a string in Python. Out of all the approaches, the approaches using re.sub() method and the replace() method have the best time complexity. Therefore, I would suggest you use these approaches in your program.
I hope you enjoyed reading this article. To learn more about python programming, you can read this article on how to remove all occurrences of a character in a list in Python. You might also like this article on how to check if a python string contains a number.
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Python remove substring from a String + Examples
In this python tutorial, we will discuss Python remove substring from a string and also cover the below points:
- Remove substring from string python regex
- Remove substring from string python DataFrame
- Python remove substring from string by index
- Remove duplicate substring from string python
- Remove the last substring from string python
- Remove multiple substrings from string python
- Remove the first substring from string python
- Remove substring from beginning of string python
- Python remove substring from a string if exists
- Remove a substring from a string python pandas
- How to remove all occurrences of a substring from a string in python
- Python remove substring from the middle of a string
Table of Contents
Python remove substring from a String
A substring is a contiguous sequence of characters. We extract these substrings using the substring method.
- When you give the substring method one number the result in the section from that position to the end of the string.
- If you have two numbers, you get the section starting at the start index up to but not including the end position.
- For example, abcdef is a string where the cd is a substring of this string.
Here is the syntax of Substring
Python remove substring from a String
- In this section, we will learn how to remove substring from a string.
- Python removes a character from a string offers multiple methods by which we can easily remove substring from a string.
- String replace()
String replace() method replaces a specified character with another specified character.
Here is the Syntax of String replace()
Let’s take an example to check how to remove substring from a string in Python.
Here is the screenshot of following given code.
This is how to remove substring from a String in Python.
Remove substring from string python regex
- In this section, we will learn how to remove substring from string python regex.
- Regular Expression is basically used for describing a search pattern so you can use regular expression for searching a specific string in a large amount of data.
- You can verify that string has a proper format or not you can find a string and replace it with another string and you can even format the data into a proper form for importing so these are all uses of the regular expression.
- Now over here I have shown you an example here.
- There is a string that is present in which they have written George is 22 and Michael is 34. So as you can see what are useful data that I can find here only name and age.
- So what I can do I can identify a pattern with the help of regular expression.
- I can convert that to a dictionary.
Let’s take an example to check how to remove substring from string python regex.
Here is the screenshot of following given code.
This is how to remove substring from string using regex in Python (python remove substring from string regex).
Remove substring from string python DataFrame
DataFrame is two dimensional and the size of the data frame is mutable potentially heterogeneous data. We can call it heterogeneous tabular data so the data structure which is a dataframe also contains a labeled axis which is rows and columns and arithmetic operation aligned on both rows and column tables. It can be thought of as a dictionary-like container.
- In this section, we will learn how to remove substring from string Python DataFrame.
- First, we have to create a DataFrame with one column that contains a string.
- Then we have to use a string replace() method to remove substring from a string in Python DataFrame.
Let’s take an example to check how to remove substring from string python DataFrame.
Here is the screenshot of following given code.
This is how to remove substring from string in Python DataFrame.
Python remove substring from string by index
Index String method is similar to the fine string method but the only difference is instead of getting a negative one with doesn’t find your argument.
- In this section, we will learn how to remove substring from stringby index.b-1.
- Remove substring from a string by index we can easily use string by slicing method.
- String Slicing returns the characters falling between indices a and b.Starting at a,a+1,a+2..till b-1.
Here is the syntax of string slicing.
Let’s take an example to check how to remove substring from string by index.
Here is the screenshot of following given code.
This is how to remove substring from string by index in Python.
Remove duplicate substring from string Python
Let’s take an example this is a given string ‘abacd’. Now you can see that ‘a’ is repeating two times and no other character is repeating. So after removing all the duplicates. The result will be a b c d’. The condition is that you need to remove all the duplicates provided the order should be maintained.
- In this section, we will learn how to remove duplicate substring from string python.
- Using set() +split() method to remove Duplicate substring.
Here is the Syntax of set() +split()
Let’s take an example to check how to remove duplicate substring from string python.
Here is the screenshot of following given code.
The above Python code to remove duplicate substring from string in Python.
Remove last substring from string python
- In this section, we will learn how to remove the last substring from string Python.
- Using the Naive method On the off chance that the first letter of the provided substring matches, we start an inner loop to check if all components from the substring match with the successive components in the main string. That is, we just check whether the whole substring is available or not.
Let’s take an example to check how to remove the last substring from string Python.
Here is the screenshot of following given code.
This is how to remove last substring from string in Python.
Remove first substring from string python
- In this section, we will learn how to remove the first substring from string python.
- Remove the first substring from the string we can easily use string by slicing method.
- String Slicing returns the characters falling between indices a and b.Starting at a,a+1,a+2..till b-1.
Here is the syntax of String Slicing.
Let’s take an example to check how to remove the first substring from string python
Here is the screenshot of following given code.
The above Python code we can use to remove first substring from string in Python.
Remove substring from beginning of string python
- In this section, we will learn how to remove substring from the beginning of string python.
- Using loop + remove() + startswith() remove substring from beginning of string.
Here is the syntax of loop + remove () +startswith()
Let’s take an example to check how to remove substring from beginning of string python.
Here is the screenshot of following given code.
Python remove substring from a string if exists
- In this section, we will learn how to remove a substring from a string if exists.
- String replace() method remove substring from a string if exists.
Here is the syntax of string replace
Let’s take an example to check how to remove substring from a string if exists
Here is the screenshot of following given code.
This is how to remove substring from a string if exists in Python.
Remove a substring from a string python pandas
Pandas is a python library that is used for data manipulation analysis and cleaning. Python pandas are well-suited for different kinds of data such as we can work on tabular data.
- In this section, we will learn how to remove a substring from a String Python pandas.
- First, we have to create a Data Frame with one Column that contains a String.
- Then we have to use a string replace() method which specified character with another specified character.
String replace() method remove a substring from a string python pandas.
Here is the syntax of String replace()
Let’s take an example to check how to remove a substring from a string Python Pandas
Here is the screenshot of following given code.
The above Python code, we can use to remove a substring from a string in python pandas.
How to remove all occurrences of a substring from a string in python
- In this section, we will learn how to remove all occurrences of a substring from a string in python.
- String translate() will change the string by replacing the character or by deleting the character. We have to mention the Unicode for the character and None as a replacement to delete it from the String.
- Use the String translate() method to remove all occurrences of a substring from a string in python.
Let’s take an example to check how to remove all occurrences of a substring from a string in python.
Here is the screenshot of following given code.
The above Python code, we can use to remove all occurrences of a substring from a string in python.
Python remove substring from the middle of a string
- In this section, we will learn how to remove substring from the middle of a string.
- The string replace() method remove the substring from the middle of a string.
Here is the syntax of String replace
Let’s take an example to check how to remove substring from the middle of a string.
Here is the screenshot of following given code
The above Python code, we can use to remove substring from the middle of a string in Python.
You may like the following Python tutorials:
In this python tutorial we learned about how to remove substring from a String in Python with the below examples:
- How to remove substring from a String in Python
- Remove substring from string python regex
- How to remove substring from string python DataFrame
- Python remove substring from string by index
- How to remove duplicate substring from string Python
- Remove last substring from string python/
- How to remove first substring from string python
- Remove substring from beginning of string python
- Python remove substring from a string if exists
- Remove a substring from a string python pandas
- How to remove all occurrences of a substring from a string in python
- Python remove substring from the middle of a string
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How do I remove a substring from the end of a string?
strip doesn’t mean "remove this substring". x.strip(y) treats y as a set of characters and strips any characters in that set from both ends of x .
On Python 3.9 and newer you can use the removeprefix and removesuffix methods to remove an entire substring from either side of the string:
The relevant Python Enhancement Proposal is PEP-616.
On Python 3.8 and older you can use endswith and slicing:
If you are sure that the string only appears at the end, then the simplest way would be to use ‘replace’:
Since it seems like nobody has pointed this on out yet:
This should be more efficient than the methods using split() as no new list object is created, and this solution works for strings with several dots.
Starting in Python 3.9 , you can use removesuffix instead:
Depends on what you know about your url and exactly what you’re tryinh to do. If you know that it will always end in ‘.com’ (or ‘.net’ or ‘.org’) then
is the quickest solution. If it’s a more general URLs then you’re probably better of looking into the urlparse library that comes with python.
If you on the other hand you simply want to remove everything after the final ‘.’ in a string then
will work. Or if you want just want everything up to the first ‘.’ then try
If you know it’s an extension, then
This works equally well with abcdc.com or www.abcdc.com or abcdc.[anything] and is more extensible.
On any Python version:
or the one-liner:
For urls (as it seems to be a part of the topic by the given example), one can do something like this:
Both will output: (‘http://www.stackoverflow’, ‘.com’)
This can also be combined with str.endswith(suffix) if you need to just split «.com», or anything specific.
DSCLAIMER This method has a critical flaw in that the partition is not anchored to the end of the url and may return spurious results. For example, the result for the URL "www.comcast.net" is "www" (incorrect) instead of the expected "www.comcast.net". This solution therefore is evil. Don’t use it unless you know what you are doing!
This is fairly easy to type and also correctly returns the original string (no error) when the suffix ‘.com’ is missing from url .
Assuming you want to remove the domain, no matter what it is (.com, .net, etc). I recommend finding the . and removing everything from that point on.
Here I’m using rfind to solve the problem of urls like abcdc.com.net which should be reduced to the name abcdc.com .
If you’re also concerned about www. s, you should explicitly check for them:
The 1 in replace is for strange edgecases like www.net.www.com
If your url gets any wilder than that look at the regex answers people have responded with.
If you mean to only strip the extension:
It works with any extension, with potential other dots existing in filename as well. It simply splits the string as a list on dots and joins it without the last element.
If you need to strip some end of a string if it exists otherwise do nothing. My best solutions. You probably will want to use one of first 2 implementations however I have included the 3rd for completeness.
For a constant suffix:
For a collection of constant suffixes the asymptotically fastest way for a large number of calls:
the final one is probably significantly faster in pypy then cpython. The regex variant is likely faster than this for virtually all cases that do not involve huge dictionaries of potential suffixes that cannot be easily represented as a regex at least in cPython.
In PyPy the regex variant is almost certainly slower for large number of calls or long strings even if the re module uses a DFA compiling regex engine as the vast majority of the overhead of the lambda’s will be optimized out by the JIT.
In cPython however the fact that your running c code for the regex compare almost certainly outweighs the algorithmic advantages of the suffix collection version in almost all cases.
Методы строк в Python
В Python у разных типов данных есть свои методы (функции), специфичные для этого типа данных. И раз уж на прошлом уроке мы начали знакомиться со строками, то никак не пройти и мимо методов строк.
Вызов метода в Python
Для вызова метода, прибавляем точку к переменной, для которой данный метод вызывается, пишем само название метода и передаем в скобочках аргументы.
Поиск подстроки в строке Python
Для поиска подстроки в строке в Python, есть четыре метода:
- find()
- rfind()
- index()
- rindex()
Метод find() ищет индекс подстроки в строке — возвращает номер позиции символа указанного в аргументах.
В случае нескольких символов идущих подряд, Python вернет позицию, с которой начинается полное совпадение.
При обращении к несуществующей подстроке, вернется значение -1.
Метод index() тоже ищет подстроку в строке по её индексу, но в случае поиска несуществующей подстроки в отличии от find(), возвращает ошибку ValueError.
Методы rfind() и rindex() ищут подстроку с конца строки — справа.
Замена символа в строке
Метод replace() заменяет одни символы на другие, где первым параметром передаем, что заменить. А во втором параметре указываем , на что заменить.
Как удалить символ из строки?
Передадим во втором параметре пустые кавычки.
Как удалить пробелы в строке?
Первым параметром указываем пробел, а вторым параметром — пустые кавычки.
Разделить строку в Python
По умолчанию метод split() разделяет строку по пробелам и преобразует строку в список. В итоге мы получили список из трех элементов.
Разделить строку можно по любому другому символу, для этого передадим нужный символ в параметрах. При этом, сам символ удаляется из списка.
# Пример 1 — разделить по тире «-«
# Пример 2 — разделить по букве «t»
Объединить строки в Python
Несмотря на то, что метод join() является не строковым методом. Мы все равно его изучим в рамках данного урока. Поскольку join() в Python выполняет противоположную функцию метода split(). Берет элементы списка и преобразует список в строку. Имя переменной, ссылающейся на список строк — единственный передаваемый параметр метода join(). Перед точкой, мы указали разделитель — пустые кавычки.
Метод join() не работает с числовыми данными. Следующая запись приведет к ошибке.
Перед использованием метода join(), следует числа привести к строкам.
Верхний регистр строки в Python
Метод upper() приводит все буквы строки к верхнему регистру, не меняя остальных символов.
Нижний регистр строки в Python
Метод lower() приводит все буквы строки к нижнему регистру.
Подсчет количества символов
Метод count() считает, сколько раз встречается подстрока в строке, указанная в параметрах.
Проверка символов в строке
Метод isalpha() проверяет, состоит ли строка только из букв и возвращает истину или ложь.
Метод isdigit() проверяет, состоит ли строка только из цифр и возвращает истину или ложь.
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