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Python: Check that a string contains only a certain set of characters

Python Regular Expression: Exercise-1 with Solution

Write a Python program to check that a string contains only a certain set of characters (in this case a-z, A-Z and 0-9).

Sample Solution:-

Python Code:

import re
def is_allowed_specific_char(string):
    charRe = re.compile(r'[^a-zA-Z0-9]')
    string = charRe.search(string)
    return not bool(string)

print(is_allowed_specific_char("ABCDEFabcdef123450")) 
print(is_allowed_specific_char("*&%@#!}{"))

Sample Output: 

True                                                                                                          
False

Pictorial Presentation:

Python: Regular Expression - Check that a string contains only a certain set of characters.
Python: Regular Expression - Check that a string contains only a certain set of characters.

Flowchart:

Flowchart: Regular Expression - Check that a string contains only a certain set of characters.

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Python: Tips of the Day

Find current directory and file's directory:

To get the full path to the directory a Python file is contained in, write this in that file:

import os 
dir_path = os.path.dirname(os.path.realpath(__file__))

(Note that the incantation above won't work if you've already used os.chdir() to change your current working directory, since the value of the __file__ constant is relative to the current working directory and is not changed by an os.chdir() call.)

To get the current working directory use

import os
cwd = os.getcwd()

Documentation references for the modules, constants and functions used above:

  • The os and os.path modules.
  • The __file__ constant
  • os.path.realpath(path) (returns "the canonical path of the specified filename, eliminating any symbolic links encountered in the path")
  • os.path.dirname(path) (returns "the directory name of pathname path")
  • os.getcwd() (returns "a string representing the current working directory")
  • os.chdir(path) ("change the current working directory to path")

Ref: https://bit.ly/3fy0R6m