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Why exactly is eval evil?
...tors:
(let ((ops '(+ *)))
(dolist (op ops)
(print (eval (list op 1 2 3)))))
That's better written as:
(let ((ops '(+ *)))
(dolist (op ops)
(print (funcall op 1 2 3))))
There are lots of examples where beginners learning Lisp think they need EVAL, but they don't need it - since expressi...
Format floats with standard json module
...der
encoder.FLOAT_REPR = lambda o: format(o, '.2f')
print(json.dumps(23.67))
print(json.dumps([23.67, 23.97, 23.87]))
emits:
23.67
[23.67, 23.97, 23.87]
as you desire. Obviously, there should be an architected way to override FLOAT_REPR so that EVERY representation of a float is under your co...
not None test in Python [duplicate]
...
1033
if val is not None:
# ...
is the Pythonic idiom for testing that a variable is not set to...
Extract subset of key-value pairs from Python dictionary object?
...t that has several key value pairs (about 16), but I am only interested in 3 of them. What is the best way (shortest/efficient/most elegant) to achieve that?
...
Python's “in” set operator
...
13
If someone implemented his class's hash function in a twisted way, this is what he may get (and deserve).
– ugoren
...
How can I multiply and divide using only bit shifting and adding?
...
answered May 5 '10 at 22:31
Andrew ToulouseAndrew Toulouse
1,09311 gold badge99 silver badges1010 bronze badges
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How can I remove a specific item from an array?
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How to concatenate twice with the C preprocessor and expand a macro as in “arg ## _ ## MACRO”?
...
Standard C Preprocessor
$ cat xx.c
#define VARIABLE 3
#define PASTER(x,y) x ## _ ## y
#define EVALUATOR(x,y) PASTER(x,y)
#define NAME(fun) EVALUATOR(fun, VARIABLE)
extern void NAME(mine)(char *x);
$ gcc -E xx.c
# 1 "xx.c"
# 1 "<built-in>"
# 1 "<command-line>"
# 1...
Python 2.7: Print to File
...
138
If you want to use the print function in Python 2, you have to import from __future__:
from __...
App Inventor 2开发计步器与定位器 - App Inventor 2 中文网 - 清泛IT论坛，有思想、有深度
...2.了解数据持久化，掌握数据存储等功能的实现；
3.通过编程实践，感受和体验利用手机自身硬件开发实用的手机应用程序。 【项目范例】
1. 情境
现在的手机都已经具有计步器及位置传感器等各种硬件传感...