# 1) data basics # numbers i = 1234 # integer f = 1.234 # float # operators a = 12 + 5 # = 17 b = 3 * 4 # = 12 c = 6 / 3 # = 2 d = 46 % 5 # = 1 (=> modulo operator) a += 1 # = 18 a -= 2 # = 16 a *= 2 # = 32 a /= 2 # = 16 a %= 5 # = 1 # text s = 'string' s = s.upper() # 'STRING' s = s.lower() # 'string' s.startswith('s') # true s.endswith('ng') # true s = s.replace('str', 'bl') # 'bling' l = s.split('i') # list ['bl', 'ng'] strings = ['s', "t", "r'i'n", 'g"s"tring', "3"] ## add the prefix r for e.g. paths to files to escape the backslash character testdoc = r'test\test.txt' ## same as : 'test\\test.txt' # list l = ['a1'] l.append('b2') l.append('c3') l[0] # 'a1' mixed = ['3', 'abc', 3, 4.56] d = {} # dictionary (key-value pairs) d = {'a' : 'blabla', 'b' : 1, 3 : 'ablabl', 4 : 12.3, 16.9 : 'dif3'} d['a'] # 'blabla' # 2) conditions, loops and functions # indentation is required !!! if 3 > 2: print('3 > 2') elif 1 == 0: print('1 = 0') else: print('else clause') if 'a' in d: print(d['a']) else: print('not found') for x in range(0, 5): # from 0 to 5 (0, 1, 2, 3 ,4) print(x) letters = ['a', 'b', 'c'] for letter in letters: print(letter) # list comprehension upper_letters = [letter.upper() for letter in letters] print(upper_letters) d = { 1:'a', 2:'b', 3:'c'} for key, value in d.iteritems(): print(str(key), value) for key in d.keys(): print('key :', str(key)) for value in d.values(): print('value :', value) def special_sum(numberlist): total = 0 for element in numberlist: if element < 5: continue # go to the next element elif total > 100: break # stop the loop else: total += element return total print(special_sum([1,2,2,4,8,50, 60])) # = 118 # 3) using os and shutil # import modules import os import shutil def setup_test(directory): if not os.path.isdir(directory): os.mkdir(directory) file1 = os.path.join(directory, 'file1_test.dll') open(file1, 'a').close() # create empty file and close it file2 = os.path.join(directory, 'file2_test.txt') open(file2, 'a').close() # 'a' creates a file for appending (doesn't overwrite) setup_test('test') # looping over files in dir and subdirs and renaming some of them def list_files(startdir): for element in os.listdir(startdir): path = os.path.join(startdir, element) if os.path.isfile(path): print(path) root, extension = os.path.splitext(path) if extension.lower() == '.dll': # add an extra extension to dll's shutil.copyfile(path, path + '.REMOVETHIS') # with os.rename you can replace the file ## os.rename(path, path + '.REMOVETHIS') else: list_files(path) startdir = r'test' list_files(startdir) # or you can loop with os.walk for root, directories, files in os.walk(startdir, topdown=True): print 'dir : %s' % root if files: print('files :') for f in files: print('\t', os.path.join(root, f)) # 4) reading, parsing and writing files def create_tab_test(inputpath): with open(inputpath, 'w') as inputfile: # 'w' creates a file for (over)writing # create some dummy content separated by tabs and with newlines at the end lines = ['\t'.join([str(1*i),str(2*i)])+'\n' for i in range(5)] # write to the file inputfile.writelines(lines) def tab_to_csv(inputpath, outputpath): # only for small files lines = [] with open(inputpath) as inputfile: for line in inputfile: line = line.replace('\n', '') columns = line.split('\t') line = ';'.join(columns) lines.append(line) with open(outputpath, 'w') as outputfile: # overwrites the outputfile if it exists outputfile.write('\n'.join(lines)) inputpath = r'test\test.txt' ## or 'D:\temp\test.txt' outputpath = r'test\test.csv' create_tab_test(inputpath) tab_to_csv(inputpath, outputpath)
Want to learn more or need some help ?
Contact me at mail@samuelbosch.com or take a look at one of the following resources:
- https://docs.python.org/3/tutorial/
- Learn Python The Hard Way by Zed A. Shaw
- A Byte of Python by Swaroop Chitlur
- Dive Into Python 3 by Mark Pilgrim
-- update --
Some suggestions by Meriam in the comments:
- Type "import this" in a python prompt
- Have a look at the style guide for python code
- Learn about exceptions
