Hello World
import __hello__Pythonic
遍历列表
array = [1, 2, 3, 4, 5]
for i in range(len(array)):
print (i, array[i])
# Pythonic
for i, item in enumerate(array):
print (i, item)对列表的操作
array = [1, 2, 3, 4, 5]
new_array = []
for item in array:
new_array.append(str(item))
# Pythonic
new_array = [str(item) for item in array]
# Generator
new_array = (str(item) for item in array)
# 函数式
new_array = map(str, array)列表推导
# 生成列表
[ i*i for i in range(10) if i % 2 == 0 ]
# 生成集合
{ i*i for i in range(10) if i % 2 == 0 }
# 生成字典
{ i:i for i in range(10) if i % 2 == 0 }上下文管理器
file = open('file', 'w')
file.write(123)
file.close()
# Pythonic
with open('file', 'w') as file:
file.write(123)条件判断
if x is True:
y = 1
else:
y = -1
# Pythonic
y = 1 if x is True else -1构造矩阵
y = [0 for _ in range(100000000)] # xrange in 2.x
# Pythonic
y = [0] * 100000000装饰器
def logic(x):
if x < 0:
return False
print (x)
return True
#Pythonic
def check_gt_zero(func):
def wrapper(x):
if x < 0:
return False
return func(x)
return wrapper
@check_gt_zero
def logic(x):
print (x)
return True变量交换
temp = y
y = x
x = temp
# Pythonic
x, y = y, x切片
array = [1, 2, 3, 4, 5]
l = len(array)
for i in range(l/2):
temp = array[l - i - 1]
array[l - i - 1] = array[i]
array[i] = temp
array = list(reversed(array))
# Pythonic
array = array[::-1]读取文件
CHUNK_SIZE = 1024
with open('test.json') as f:
chunk = f.read(CHUNK_SIZE)
while chunk:
if chunk:
print(chunk)
chunk = f.read(CHUNK_SIZE)
from functools import partial
# Pythonic
with open('test.json') as f:
for piece in iter(partial(f.read, CHUNK_SIZE), ''):
print (piece)
# Lambda
with open('test.json') as f:
for piece in iter(lambda: f.read(CHUNK_SIZE), ''):
print (piece)for-else和try-else语法
is_for_finished = True
try:
for item in array:
print (item)
# raise Exception
except:
is_for_finished = False
if is_for_finished is True:
print ('complete')
# Pythonic
for item in array:
print (item)
# raise Exception
else:
print ('complete')
try:
print ('try')
# raise Exception
except Exception:
print ('exception')
else:
print ('complete')函数参数解压
def draw_point(x, y):
# do some magic
point_foo = (3, 4)
point_bar = {'y': 3, 'x': 2}
draw_point(*point_foo)
draw_point(**point_bar)列表/元祖解压
first, second, *rest = (1,2,3,4,5,6,7,8)"Print To"语法
# 2.x
print >> open("myfile", "w"), "hello world"
# 3.x
print ("hello world", file=open("myfile", "w"))字典缺省值
d = {}
try:
d['count'] = d['count'] + 1
except KeyError:
d['count'] = 0
# Pythonic
d['count'] = d.get('count', 0) + 1链式比较符
if x < 100 and x > 0:
print(x)
# Pythonic
if 0 < x < 100:
print(x)多行字符串
s = ("longlongstringiii"
"iiiiiiiii"
"iiiiiii")
print(s)in表达式
if 'string'.find('ring') > 0:
print ('find')
# Pythonic
if 'ring' in 'string':
print ('find')
for r in ['ring', 'ring1', 'ring2']:
if r == 'ring':
print ('find')
# Pythonic
if 'ring' in ['ring', 'ring1', 'ring2']:
print('find')字符串连接
array = ['a', 'b', 'c', 'd', 'e']
s = array[0]
for char in array[1:]:
s += ',' + char
# Pythonic
s = ','.join(array)列表合并字典
keys = ['a', 'b', 'c']
values = [1, 2, 3]
d = {}
for key, value in zip(keys, values):
d[key] = value
# Better
d = dict(zip(keys, values))
# Pythonic
d = {key: value for key, value in zip(keys, values)}all和any
flag = True
for cond in conditions:
if cond is False:
flag = False
break
# Pythonic
flag = all(conditions)
flag = False
for cond in conditions:
if cond is True:
flag = True
break
# Pythonic
flag = any(conditions)or
not_null_string = '' or 'string1' or 'string2'
# string1方法提取
for item in ['b', 'c']:
array.append(item)
# Faster
append = array.append
for item in ['b', 'c']:
append(item)单例模式
from [module] import [single_instance]性能排查
python -m cProfile test.py格式化一个json文件
python -m json.tool test.json管道
echo '{"json":"obj"}' | python -m json.tool开启本地目录的HTTP服务器
2.x
python -m SimpleHTTPServer 80803.x
python3 -m http.server 8080在Python使用花括号块
from __future__ import bracesPython之禅
In [1]: import this
The Zen of Python, by Tim Peters
Beautiful is better than ugly.
Explicit is better than implicit.
Simple is better than complex.
Complex is better than complicated.
Flat is better than nested.
Sparse is better than dense.
Readability counts.
Special cases aren't special enough to break the rules.
Although practicality beats purity.
Errors should never pass silently.
Unless explicitly silenced.
In the face of ambiguity, refuse the temptation to guess.
There should be one-- and preferably only one --obvious way to do it.
Although that way may not be obvious at first unless you're Dutch.
Now is better than never.
Although never is often better than *right* now.
If the implementation is hard to explain, it's a bad idea.
If the implementation is easy to explain, it may be a good idea.
Namespaces are one honking great idea -- let's do more of those!XKCD漫画
import antigravity一张图理解Type和Object
