Генератор строк в питоне

Generate Random Strings and Passwords in Python

In this lesson, you will learn how to create a random string and passwords in Python.

Table of contents

String Constants

Below is the list of string constants you can use to get a different set of characters as a source for creating a random string.

Constant	Description
ascii_lowercase	Contain all lowercase letters
ascii_uppercase	Contain all uppercase letters
ascii_letters	Contain both lowercase and uppercase letters
digits	Contain digits ‘0123456789’.
punctuation	All special symbols !”#$%&'()*+,-./:;?@[\]^_`<|>~.
whitespace	Includes the characters space, tab, linefeed, return, formfeed, and vertical tab [^ \t\n\x0b\r\f]
printable	characters that are considered printable. This is a combination of constants digits , letters , punctuation , and whitespace .

String constants

How to Create a Random String in Python

We can generate the random string using the random module and string module. Use the below steps to create a random string of any length in Python.

1. Import string and random module The string module contains various string constant which contains the ASCII characters of all cases. It has separate constants for lowercase, uppercase letters, digits, and special symbols, which we use as a source to generate a random string.
   Pass string constants as a source of randomness to the random module to create a random string
2. Use the string constant ascii_lowercase The string.ascii_lowercase returns a list of all the lowercase letters from ‘a’ to ‘z’. This data will be used as a source to generate random characters.
3. Decide the length of a string Decide how many characters you want in the resultant string.
4. Use a for loop and random choice() function to choose characters from a source Run a for loop till the decided string length and use the random choice() function in each iteration to pick a single character from the string constant and add it to the string variable using a join() function. print the final string after loop competition
5. Generate a random Password Use the string.ascii_letters , string.digits , and string.punctuation constants together to create a random password and repeat the first four steps.

Example to generate a random string of any length

import random import string def get_random_string(length): # choose from all lowercase letter letters = string.ascii_lowercase result_str = ''.join(random.choice(letters) for i in range(length)) print("Random string of length", length, "is:", result_str) get_random_string(8) get_random_string(6) get_random_string(4)

Random string of length 8 is: ijarubtd Random string of length 6 is: ycfxbs Random string of length 4 is: dpla

• The random choice() function is used to choose a single item from any sequence and it can repeat characters.
• The above random strings contain all lower case letters. If you want only the uppercase letters, then use the string.ascii_uppercase constant instead in the place of a string.ascii_lowercase .

Random String of Lower Case and Upper Case Letters

In Python, to generate a random string with the combination of lowercase and uppercase letters, we need to use the string.ascii_letters constant as the source. This constant contains all the lowercase and uppercase letters.

import random import string def get_random_string(length): # With combination of lower and upper case result_str = ''.join(random.choice(string.ascii_letters) for i in range(length)) # print random string print(result_str) # string of length 8 get_random_string(8) get_random_string(8)

Random string of specific letters

If you wanted to generate a random string from a fixed set of characters, please use the following example.

import random # Random string of length 5 result_str = ''.join((random.choice('abcdxyzpqr') for i in range(5))) print(result_str) # Output ryxay

Random String without Repeating Characters

Note: The choice() method can repeat characters. If you don’t want repeated characters in a resultant string, then use the random.sample() method.

import random import string for i in range(3): # get random string of length 6 without repeating letters result_str = ''.join(random.sample(string.ascii_lowercase, 8)) print(result_str)

wxvdkbfl ztondpef voeduias

Warning : As you can see in the output, all characters are unique, but it is less secure because it will reduce the probability of combinations of letters because we are not allowing repetitive letters and digits.

Create Random Password with Special characters, letters, and digits

A password that contains a combination of characters, digits, and special symbols is considered a strong password.

Assume, you want to generate a random password like: –

We can generate a random string password in Python with letters, special characters, and digits using the following two ways.

• Combine the following three constants and use them as a data source for the random.choice() function to select random characters from it.
  • string.ascii_letters : To include letters from a-z and A-Z
  • string.digits : To include digits from 1 to 10
  • string.punctuation : to get special symbols

  import random import string # get random password pf length 8 with letters, digits, and symbols characters = string.ascii_letters + string.digits + string.punctuation password = ''.join(random.choice(characters) for i in range(8)) print("Random password is:", password)

  Random password is: 6(I3goZ>

  Using the string.printable

  import random import string password = ''.join(random.choice(string.printable) for i in range(8)) print("Random password is:", password)

  Random password is: hY*34jj.

  Random password with a fixed count of letters, digits, and symbols

  It is a widespread use case that passwords must contain some count of digits and special symbols.

  Let’s see how to generate a random password that contains at least one lowercase letter, one uppercase letter, one digit, and one special symbol.

  • First, select the number of random lowercase and uppercase letters specified
  • Next, choose the number of random digits
  • Next, choose the number of special symbols
  • Combine both letters, digits, and special symbols into a list
  • At last shuffle the list
  • Convert list back to a string

  import random import string def get_random_password(): random_source = string.ascii_letters + string.digits + string.punctuation # select 1 lowercase password = random.choice(string.ascii_lowercase) # select 1 uppercase password += random.choice(string.ascii_uppercase) # select 1 digit password += random.choice(string.digits) # select 1 special symbol password += random.choice(string.punctuation) # generate other characters for i in range(6): password += random.choice(random_source) password_list = list(password) # shuffle all characters random.SystemRandom().shuffle(password_list) password = ''.join(password_list) return password print("First Random Password is ", get_random_password()) # output qX49>]Ru!( print("Second Random Password is ", get_random_password()) # Output 3nI0.V#[T

  Generate a secure random string and password

  Above all, examples are not cryptographically secure. The cryptographically secure random generator generates random data using synchronization methods to ensure that no two processes can obtain the same data simultaneously.

  If you are producing random passwords or strings for a security-sensitive application, then you must use this approach.

  If you are using Python version less than 3.6, then use the random.SystemRandom().choice() function instead of random.choice() .

  If you are using a Python version higher than 3.6 you can use the secrets module to generate a secure random password.

  Use secrets.choice() function instead of random.choice()

  import secrets import string # secure random string secure_str = ''.join((secrets.choice(string.ascii_letters) for i in range(8))) print(secure_str) # Output QQkABLyK # secure password password = ''.join((secrets.choice(string.ascii_letters + string.digits + string.punctuation) for i in range(8))) print(password) # output 4x]>@;4)

  Generate a random alphanumeric string of letters and digits

  We often want to create a random string containing both letters and digits such as ab23cd, jkml98, 87thki. In such cases, we use the string.ascii_letters and string.digits constants to get the combinations of letters and numbers in our random string.

  Now, let’s see the to create a random string with the combination of a letter from A-Z, a-z, and digits 0-9.

  import random import string # get random string of letters and digits source = string.ascii_letters + string.digits result_str = ''.join((random.choice(source) for i in range(8))) print(result_str) # Output vZkOkL97

  Random alphanumeric string with a fixed count of letters and digits

  For example, I want to create a random alpha-numeric string that contains 5 letters and 3 numbers.

  import random import string def get_string(letters_count, digits_count): letters = ''.join((random.choice(string.ascii_letters) for i in range(letters_count))) digits = ''.join((random.choice(string.digits) for i in range(digits_count))) # Convert resultant string to list and shuffle it to mix letters and digits sample_list = list(letters + digits) random.shuffle(sample_list) # convert list to string final_string = ''.join(sample_list) print('Random string with', letters_count, 'letters', 'and', digits_count, 'digits', 'is:', final_string) get_string(5, 3) # Output get_string(5, 3) get_string(6, 2) # Output Random string with 6 letters and 2 digits is: 7DeOCm5t 

  First random alphanumeric string is: v809mCxH Second random alphanumeric string is: mF6m1TRk

  Generate a random string token

  The above examples depend on String constants and random module functions. There are also other ways to generate a random string in Python. Let see those now.

  We can use secrets.token_hex() to get a secure random text in hexadecimal format.

  import secrets print("Secure hexadecimal string token", secrets.token_hex(32))

  Secure hexadecimal string token 25cd4dd7bedd7dfb1261e2dc1489bc2f046c70f986841d3cb3d59a9626e0d802

  Generate universally unique secure random string Id

  The random string generated using a UUID module is suitable for the Cryptographically secure application. The UUID module has various functions to do this. Here in this example, we are using a uuid4() function to generate a random string Id.

  import uuid stringId = uuid.uuid4() print("Secure unique string id", stringId) # Output 0682042d-318e-45bf-8a16-6cc763dc8806

  Use the StringGenerator module to generate a random string

  The StringGenerator module is not a part of a standard library. However, if you want you can install it using pip and start using it.

  • pip install StringGenerator .
  • Use a render() function of StringGenerator to generate randomized strings of characters using a template

  import strgen random_str = strgen.StringGenerator("[\w\d]").render() print(random_str) # Output 4VX1yInC9S random_str2 = strgen.StringGenerator("[\d]&[\w]&[\p]").render() print(random_str2) # output "C01N=10

  Next Steps

  I want to hear from you. What do you think of this article? Or maybe I missed one of the ways to generate random string in Python. Either way, let me know by leaving a comment below.

  Also, try to solve the random module exercise and quiz to have a better understanding of working with random data in Python.

  Practice Problem

  Create a random alphanumeric string of length ten that must contain at least four digits. For example, the output can be anything like 1o32WzUS87, 1P56X9Vh87

  import random import string digits = string.digits letter_digit_list = list(string.digits + string.ascii_letters) # shuffle random source of letters and digits random.shuffle(letter_digit_list) # first generate 4 random digits sample_str = ''.join((random.choice(digits) for i in range(4))) # Now create random string of length 6 which is a combination of letters and digits # Next, concatenate it with sample_str sample_str += ''.join((random.choice(letter_digit_list) for i in range(6))) aList = list(sample_str) random.shuffle(aList) final_str = ''.join(aList) print("Random String:", final_str) # Output 81OYQ6D430

  Did you find this page helpful? Let others know about it. Sharing helps me continue to create free Python resources.

  About Vishal

  I’m Vishal Hule, Founder of PYnative.com. I am a Python developer, and I love to write articles to help students, developers, and learners. Follow me on Twitter

  Related Tutorial Topics:

  Python Exercises and Quizzes

  Free coding exercises and quizzes cover Python basics, data structure, data analytics, and more.

  • 15+ Topic-specific Exercises and Quizzes
  • Each Exercise contains 10 questions
  • Each Quiz contains 12-15 MCQ

  Источник

  Читайте также:  Java unmappable character error