You create a new key/value pair on a dictionary by assigning a value to that key d = {‘key’: ‘value’} print(d) # {‘key’: ‘value’} d[‘mynewkey’] = ‘mynewvalue’ print(d) # {‘key’: ‘value’, ‘mynewkey’: ‘mynewvalue’} If the key doesn’t exist, it’s added and points to that value. If it exists, the current value it points to is … Read more
shutil has many methods you can use. One of which is: import shutil shutil.copyfile(src, dst) # 2nd option shutil.copy(src, dst) # dst can be a folder; use shutil.copy2() to preserve timestamp Copy the contents of the file named src to a file named dst. Both src and dst need to be the entire filename of … Read more
Python 3.7+ or CPython 3.6 Dicts preserve insertion order in Python 3.7+. Same in CPython 3.6, but it’s an implementation detail. >>> x = {1: 2, 3: 4, 4: 3, 2: 1, 0: 0} >>> {k: v for k, v in sorted(x.items(), key=lambda item: item[1])} {0: 0, 2: 1, 1: 2, 4: 3, 3: 4} … Read more
Decode the bytes object to produce a string: >>> b”abcde”.decode(“utf-8”) ‘abcde’ The above example assumes that the bytes object is in UTF-8, because it is a common encoding. However, you should use the encoding your data is actually in!
Alex summarized well but, surprisingly, was too succinct. First, let me reiterate the main points in Alex’s post: The default implementation is useless (it’s hard to think of one which wouldn’t be, but yeah) __repr__ goal is to be unambiguous __str__ goal is to be readable Container’s __str__ uses contained objects’ __repr__ Default implementation is … Read more
os.listdir() returns everything inside a directory — including both files and directories. os.path‘s isfile() can be used to only list files: from os import listdir from os.path import isfile, join onlyfiles = [f for f in listdir(mypath) if isfile(join(mypath, f))] Alternatively, os.walk() yields two lists for each directory it visits — one for files and … Read more
DataFrame.iterrows is a generator which yields both the index and row (as a Series): import pandas as pd df = pd.DataFrame({‘c1’: [10, 11, 12], ‘c2’: [100, 110, 120]}) df = df.reset_index() # make sure indexes pair with number of rows for index, row in df.iterrows(): print(row[‘c1’], row[‘c2’]) 10 100 11 110 12 120
From Python Documentation: An except clause may name multiple exceptions as a parenthesized tuple, for example except (IDontLikeYouException, YouAreBeingMeanException) as e: pass Or, for Python 2 only: except (IDontLikeYouException, YouAreBeingMeanException), e: pass Separating the exception from the variable with a comma will still work in Python 2.6 and 2.7, but is now deprecated and does … Read more
Use datetime: >>> import datetime >>> now = datetime.datetime.now() >>> now datetime.datetime(2009, 1, 6, 15, 8, 24, 78915) >>> print(now) 2009-01-06 15:08:24.789150 For just the clock time without the date: >>> now.time() datetime.time(15, 8, 24, 78915) >>> print(now.time()) 15:08:24.789150 To save typing, you can import the datetime object from the datetime module: >>> from datetime … Read more
Use the in operator: if “blah” not in somestring: continue