pg_config executable not found
pg_config is in postgresql-devel (libpq-dev in Debian/Ubuntu, libpq-devel on Centos/Fedora/Cygwin/Babun.)
python
If Python is interpreted, what are .pyc files?
I’ve been given to understand that Python is an interpreted language… This popular meme is incorrect, or, rather, constructed upon a misunderstanding of (natural) language levels: a similar mistake would be to say “the Bible is a hardcover book”. Let me explain that simile… “The Bible” is “a book” in the sense of being a … Read more
How to drop rows of Pandas DataFrame whose value in a certain column is NaN
Don’t drop, just take the rows where EPS is not NA: df = df[df[‘EPS’].notna()]
How to add a new column to an existing DataFrame?
Edit 2017 As indicated in the comments and by @Alexander, currently the best method to add the values of a Series as a new column of a DataFrame could be using assign: df1 = df1.assign(e=pd.Series(np.random.randn(sLength)).values) Edit 2015 Some reported getting the SettingWithCopyWarning with this code. However, the code still runs perfectly with the current pandas … Read more
Getting key with maximum value in dictionary?
max(stats, key=stats.get)
How to read a text file into a string variable and strip newlines?
You could use: with open(‘data.txt’, ‘r’) as file: data = file.read().replace(‘\n’, ”) Or if the file content is guaranteed to be one-line with open(‘data.txt’, ‘r’) as file: data = file.read().rstrip()
Why do people write #!/usr/bin/env python on the first line of a Python script?
If you have several versions of Python installed, /usr/bin/env will ensure the interpreter used is the first one on your environment’s $PATH. The alternative would be to hardcode something like #!/usr/bin/python; that’s ok, but less flexible. In Unix, an executable file that’s meant to be interpreted can indicate what interpreter to use by having a … Read more
Running shell command and capturing the output
In all officially maintained versions of Python, the simplest approach is to use the subprocess.check_output function: >>> subprocess.check_output([‘ls’, ‘-l’]) b’total 0\n-rw-r–r– 1 memyself staff 0 Mar 14 11:04 files\n’ check_output runs a single program that takes only arguments as input.1 It returns the result exactly as printed to stdout. If you need to write input … Read more
Display number with leading zeros
In Python 2 (and Python 3) you can do: number = 1 print(“%02d” % (number,)) Basically % is like printf or sprintf (see docs). For Python 3.+, the same behavior can also be achieved with format: number = 1 print(“{:02d}”.format(number)) For Python 3.6+ the same behavior can be achieved with f-strings: number = 1 print(f”{number:02d}”)
Create a Pandas Dataframe by appending one row at a time
You can use df.loc[i], where the row with index i will be what you specify it to be in the dataframe. >>> import pandas as pd >>> from numpy.random import randint >>> df = pd.DataFrame(columns=[‘lib’, ‘qty1’, ‘qty2’]) >>> for i in range(5): >>> df.loc[i] = [‘name’ + str(i)] + list(randint(10, size=2)) >>> df lib qty1 … Read more