The following is a list of some of the important methods/functions in Python with descriptions that you should know to understand this article.
- len() – It is used to count number of elements(items/characters) of iterables like list, tuple, string, dictionary etc.
- str() – It is used to transform data value(integers, floats, list) into string.
- abspath() – It returns the absolute path of the file/directory name passed as an argument.
- enumerate() – Returns an enumerate object for the passed iterable that can be used to iterate over the items of iterable with an access to their indexes.
- list() – It is used to create a list by using an existing iterable(list, tuple, dictionary, set).
- listdir() – It is used to list the directory contents. The path of directory is passed as an argument.
- isfile() – It checks whether the passed parameter denotes the path to a file. If yes then returns True otherwise False
- isdir() – It checks whether the passed parameter denotes the path to a directory. If yes then returns True otherwise False
- append() – It is used to append items on list.
Please see the below code executed on interactive Python terminal to have a quick walk through on the usages of above functions/methods.
>>> nums = [1,2,3,4,5] # list >>> name = "Alexander">>> details = {"name": "Hemkesh", "age": 23, "active": True} >>> >>> # Using len() ... >>> len(nums) 5>>> len(name) 9>>> len(details) 3>>> >>> # Using str() ... >>> str(12) '12'>>> str(nums) '[1, 2, 3, 4, 5]'>>> str(details) "{'active': True, 'age': 23, 'name': 'Hemkesh'}">>> >>> # Using abspath() ... >>> import os >>> os.listdir(".") ['Django', 'Prep', 'python-the-snake'] >>> os.path.abspath("./Django") # pass ".\Django" on windows '/Users/admin/projects/Python/Django'>>> os.path.abspath("Django") '/Users/admin/projects/Python/Django'>>> >>> # Using enumerate() ... >>> enumerate(nums) <enumerate object at 0x100620b90> >>> >>> for index, item in enumerate(nums): ... print index, item ... 0 11 22 33 44 5>>> >>> # Using list() ... >>> list() [] >>> list(details ) ['active', 'age', 'name'] >>> list(name) ['A', 'l', 'e', 'x', 'a', 'n', 'd', 'e', 'r'] >>> >>> # Using isfile() & isdir() ... >>> os.path.isdir("Django") True>>> os.path.isfile("Django") False>>> >>> os.path.isdir("./python-the-snake/README.md") False>>> os.path.isfile("./python-the-snake/README.md") True>>> >>> # Using append() ... >>> nums.append(12) >>> nums [1, 2, 3, 4, 5, 12] >>> nums.append(67) >>> nums [1, 2, 3, 4, 5, 12, 67] >>> >>> # Don't press "Run on IDE" button available on right. You will get error ... # as the statements are already executed on interactive terminal. ... >>> |
Path structure on different OS
Windows uses \ (back slash) as a path separator, eg. C:\Users\Desktop\
Linux based system like MAC OS X, Linux uses / (forward slash), eg. /Users/Desktop/
Let’s have a quick overview the working of above methods and functions as we are using this in our final program.
# Python version : 2.7.12 # len() # To count number of items in a list # To count number of characters in a string evens = [ 2, 34, 6, 8, 10] print len(evens) city = "Bangalore"print len(city), "\n" # str() : Converting into string representation odds = [ 1, 3, 67, 45, 83, 59] year = 2017 print odds print str(odds) + " A list.\n" print year print str(year) + " A year.\n" # enumerate() : iterating over index & value of a list for (index, item) in enumerate(odds): print index, item # abspath() : Getting absolute path of passed argument(path) import os absolute_path = os.path.abspath(".") print "\n", absolute_path, "\n" # isdir() : To check if passed argument is valid directory path answer = os.path.isdir("/Users/admin/Desktop/js") print answer # isfile() : To check if the passed argument is valid file path answer = os.path.isfile("/Users/admin/Desktop/js/array.js") print answer, "\n" # list() : To create list details = { "name":"Rojert Rendrick", "age":24, "city":"Bangalore" } keys = list( details ) print keys, "\n" # append() : Appending items to list print evens evens.append(98) evens.append(64) print evens, "\n" # repetition operator(*) on strings print "Python"*3print "#"*20 |
Output:
5 9 [1, 3, 67, 45, 83, 59] [1, 3, 67, 45, 83, 59] A list. 2017 2017 A year. 0 1 1 3 2 67 3 45 4 83 5 59 /Users/admin/projects/Python/PythonFiles True True ['city', 'age', 'name'] [2, 34, 6, 8, 10] [2, 34, 6, 8, 10, 98, 64] PythonPythonPython ####################
There are number of Python files & directories inside /Users/admin/projects/Python/PythonFiles, we will list out all these.
Suppose current working directory is /Users/admin/projects/Python/Django/E-Commerce-projects/ecommerce-2/src, which has some files and folders inside it.
In your case, it will be different. You will only need to pass the exact path of the directory that you want to list out.
The following is the python code to display all the files and directories based on the passed absolute or relative path.
If path is not specified in the calling statement then the contents of current working directory will be displayed.
# This Python code is for Python version : 2.7.12 def show_directories(dir_list, path): """ A function that lists the directories """ import os s = "%s%d%s"%("\n", len(dir_list), " directories of " + os.path.abspath(path)) l = len(s) print s print "="*l for index, dir in enumerate(dir_list): print str(index+1) + ") ", dir def show_files(file_list, path): """ A function that lists the files """ import os s = "%s%d%s"%("\n", len(file_list), " files of " + os.path.abspath(path)) l = len(s) print s print "="*l for index, file in enumerate(file_list): print str(index+1) + ") ", file def show_cwd_contents( path="." ): # A function that calls 2 functions to separately # listing out directories and files. # It takes a default argument as cwd(.). We can # pass other paths too. import os f_list = [] d_list = list() try: for f in os.listdir(path): if os.path.isfile(os.path.join(path, f)): f_list.append(f) else: if os.path.isdir(os.path.join(path, f)): d_list.append(f) except: print "\nError, once check the path" return show_files(f_list, path) show_directories(d_list, path) if __name__ == "__main__": # If this module is imported in other module then # we need to separately call show_cwd_contents() Or # show_cwd_contents(path). show_cwd_contents() show_cwd_contents("/Users/admin/projects/Python/PythonFiles") |
Output:
5 files of /Users/admin/projects/Python/Django/E-Commerce-projects/ecommerce-2/src =================================================================================== 1) .gitignore 2) db.sqlite3 3) manage.py 4) requirements.txt 5) todo.txt 5 directories of /Users/admin/projects/Python/Django/E-Commerce-projects/ecommerce-2/src ========================================================================================= 1) ecommerce2 2) newsletter 3) products 4) static_in_pro 5) templates 70 files of /Users/admin/projects/Python/PythonFiles ===================================================== 1) 2_list_iterators.py 2) app.py 3) class_script_exec.py 4) class_variables.py 5) date_and_time.py 6) datetime.txt 7) dict.py 8) dictionary.py 9) django_home.html 10) error_handling.py 11) error_handling_output.py 12) error_handling_output.txt 13) execution_pickle.py 14) fb_task.py 15) for.py 16) gfg_sum_of_primes_in_numbers.py 17) hackerrank_numbers.py 18) hck_addition_aint_simple.py 19) hck_biased_chandan.py 20) hck_c_counts.py 21) hck_c_counts2.py 22) hck_c_counts3.py 23) hck_cool_numbers.py 24) hck_earth_fans.py 25) hck_earth_fans_2.py 26) hck_earth_fans_3.py 27) hck_earth_fans_final_on_28_dec_2016.py 28) hck_Little_Jhool_and_psychic_powers.py 29) hck_lonely_monk.py 30) hck_lonely_monk_orig.py 31) hck_maximum_AND.py 32) hck_min_max_problem.py 33) hck_monk_and_power_of_time.py 34) hck_numbers_rotation.py 35) hck_palindomic_numbers.py 36) hck_print_hackerearth.py 37) hck_print_hackerearth_2_way.py 38) hck_range_query.py 39) hck_recursive_functions.py 40) hck_recursive_sums.py 41) hck_strange_addition.py 42) hck_sum_of_numbers.py 43) interactive_img_resolutions.txt 44) json.py 45) json.pyc 46) katyperry.py 47) lambda_expression.py 48) linked_list_delete_nodes_at_front.py 49) linked_list_delete_nodes_at_front_output.txt 50) linked_list_is_palindrome_gfg.py 51) linked_list_is_palindrome_gfg_output.text 52) linked_list_is_palindrome_gfg_testing.py 53) linked_list_node_deletion_from_any_position.txt 54) linked_list_node_deletion_from_end.py 55) linked_list_node_deletion_from_end_output.txt 56) linked_list_node_deletion_from_middle.py 57) linked_list_node_insertion_at_beginning.py 58) linked_list_node_insertion_at_end.py 59) linked_list_node_insertion_at_middel_output.txt 60) linked_list_node_insertion_at_middle.py 61) map.py 62) merge_lists.py 63) mufeez_android_interview.py 64) python_for_loops.py 65) python_for_loops2.py 66) remove_dupliates.py 67) show_dir_and_files.py 68) show_dir_and_files_test.py 69) smarika_urllib_python2.7.10.py 70) while.py 2 directories of /Users/admin/projects/Python/PythonFiles ========================================================== 1) socket_programming 2) wx
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