For non-negative (unsigned) integers only, use isdigit(): >>> a = “03523” >>> a.isdigit() True >>> b = “963spam” >>> b.isdigit() False Documentation for isdigit(): Python2, Python3 For Python 2 Unicode strings: isnumeric().
Yep, using the staticmethod decorator: class MyClass(object): @staticmethod def the_static_method(x): print(x) MyClass.the_static_method(2) # outputs 2 Note that some code might use the old method of defining a static method, using staticmethod as a function rather than a decorator. This should only be used if you have to support ancient versions of Python (2.2 and 2.3): … Read more
To pad strings: >>> n = ‘4’ >>> print(n.zfill(3)) 004 To pad numbers: >>> n = 4 >>> print(f'{n:03}’) # Preferred method, python >= 3.6 004 >>> print(‘%03d’ % n) 004 >>> print(format(n, ’03’)) # python >= 2.6 004 >>> print(‘{0:03d}’.format(n)) # python >= 2.6 + python 3 004 >>> print(‘{foo:03d}’.format(foo=n)) # python >= 2.6 … Read more
Set the mode in open() to “a” (append) instead of “w” (write): with open(“test.txt”, “a”) as myfile: myfile.write(“appended text”) The documentation lists all the available modes.
Empty strings are “falsy” (python 2 or python 3 reference), which means they are considered false in a Boolean context, so you can just do this: if not myString: This is the preferred way if you know that your variable is a string. If your variable could also be some other type then you should … Read more
Try the method rstrip() (see doc Python 2 and Python 3) >>> ‘test string\n’.rstrip() ‘test string’ Python’s rstrip() method strips all kinds of trailing whitespace by default, not just one newline as Perl does with chomp. >>> ‘test string \n \r\n\n\r \n\n’.rstrip() ‘test string’ To strip only newlines: >>> ‘test string \n \r\n\n\r \n\n’.rstrip(‘\n’) ‘test … Read more
The best way to do this in Pandas is to use drop: df = df.drop(‘column_name’, axis=1) where 1 is the axis number (0 for rows and 1 for columns.) To delete the column without having to reassign df you can do: df.drop(‘column_name’, axis=1, inplace=True) Finally, to drop by column number instead of by column label, … Read more
The del statement removes an element: del d[key] Note that this mutates the existing dictionary, so the contents of the dictionary changes for anybody else who has a reference to the same instance. To return a new dictionary, make a copy of the dictionary: def removekey(d, key): r = dict(d) del r[key] return r The … Read more
It’s because any iterable can be joined (e.g, list, tuple, dict, set), but its contents and the “joiner” must be strings. For example: ‘_’.join([‘welcome’, ‘to’, ‘stack’, ‘overflow’]) ‘_’.join((‘welcome’, ‘to’, ‘stack’, ‘overflow’)) ‘welcome_to_stack_overflow’ Using something other than strings will raise the following error: TypeError: sequence item 0: expected str instance, int found
If you only want a single item’s count, use the count method: >>> [1, 2, 3, 4, 1, 4, 1].count(1) 3 Important: this is very slow if you are counting multiple different items Each count call goes over the entire list of n elements. Calling count in a loop n times means n * n … Read more