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Postgres: How to do Composite keys?
..."tags.tag_id"
NOTICE: CREATE TABLE / PRIMARY KEY will create implicit index "tags_pkey" for table "tags"
CREATE TABLE
pg=> \d tags
Table "public.tags"
Column | Type | Modifiers
------...
How to disable GCC warnings for a few lines of code
...n GCC and Clang.
Consider the following Makefile
CPPFLAGS:=-std=c11 -W -Wall -pedantic -Werror
.PHONY: all
all: puts
for building the following puts.c source code
#include <stdio.h>
int main(int argc, const char *argv[])
{
while (*++argv) puts(*argv);
return 0;
}
It will not c...
How do I get the number of elements in a list?
...turns 3.
Explanation
Everything in Python is an object, including lists. All objects have a header of some sort in the C implementation.
Lists and other similar builtin objects with a "size" in Python, in particular, have an attribute called ob_size, where the number of elements in the object is...
Where should signal handlers live in a django project?
...
I actually like to make them classmethods of the model itself. That keeps everything within one class, and means you don't have to worry about importing anything.
...
How to find all occurrences of a substring?
Python has string.find() and string.rfind() to get the index of a substring in a string.
20 Answers
...
Pandas: Setting no. of max rows
...display
import numpy as np
import pandas as pd
n = 100
foo = pd.DataFrame(index=range(n))
foo['floats'] = np.random.randn(n)
with pd.option_context("display.max_rows", foo.shape[0]):
display(foo)
pandas.option_context is available since pandas 0.13.1 (pandas 0.13.1 release notes).
According ...
How do I correctly clean up a Python object?
...it close() statement is that you have to worry about people forgetting to call it at all or forgetting to place it in a finally block to prevent a resource leak when an exception occurs.
To use the with statement, create a class with the following methods:
def __enter__(self)
def __exit__(self...
What does the “yield” keyword do?
... list, you can read its items one by one. Reading its items one by one is called iteration:
>>> mylist = [1, 2, 3]
>>> for i in mylist:
... print(i)
1
2
3
mylist is an iterable. When you use a list comprehension, you create a list, and so an iterable:
>>> mylist = [...
How can you set class attributes from variable arguments (kwargs) in python
...riable number of arguments and then sets them as class attributes conditionally.
10 Answers
...
Python class inherits object
... so are numerous, to list some of them:
Support for descriptors. Specifically, the following constructs are made possible with descriptors:
classmethod: A method that receives the class as an implicit argument instead of the instance.
staticmethod: A method that does not receive the implicit ar...