This article serves as a record of some of the tricks encountered in the use of python, some of which are written by myself, some of which are built-in functions of python, and some of which are taken from the Internet. In this record, only for backup and forgetting when easy to find.
This article will continue to be updated to record only a few commonly used but never memorable codes or modules.
Console operation
Console does not flip back
os.system('pause')
Get the console size
rows, columns = os.popen('stty size', 'r').read().split()
Input and output control
Solve the problem of Chinese scrambling in input prompts
raw_input(unicode('Please enter text','utf-8').encode('gbk'))
Format output
print a.prettify()
Accept multi-line input
text=""
while 1:
data=raw_input(">>")
if data.strip()=="stop":
break
text+="%s\n" % data
print text
---------------------------
>>1
>>2
>>3
>>stop
1
2
3
Peer output
Print '%s' % a, Print '%s \r' % a
Standard Input and Output
sys.stdout.write("input") standard input
sys.stdout.flush() refresh buffer
The function of print is similar to that of sys.stdout.write, because print in 2.x by default specifies output to standard output (sys.stdout).
If you are still confused in the world of programming, you can join our Python Learning button qun: 784758214 to see how our predecessors learned. Exchange of experience. From basic Python script to web development, crawler, django, data mining, zero-base to actual project data are sorted out. To every Python buddy! Share some learning methods and small details that need attention. Click to join us. python learner gathering place
Color control
Console color control (for windows)
WConio.textcolor(WConio.YELLOW) print "yellow" WConio.textcolor(WConio.BLUE) print "blue"
Output color control (full platform)
red = '\033[1;31m' green = '\033[1;32m' yellow = '\033[1;33m' white = '\033[1;37m' reset = '\033[0m' print red+"color is red"+reset print green+"color is green"+reset
Progress bar control
Scheme 1
from __future__ import division
import sys,time
j = '#'
for i in range(1,61):
j += '#'
sys.stdout.write(str(int((i/60)*100))+'% ||'+j+'->'+"\r")
sys.stdout.flush()
time.sleep(0.1)
Option two
import sys
import time
for i in range(1,61):
sys.stdout.write('#'+'->'+"\b\b")
sys.stdout.flush()
time.sleep(0.5)
Option three
from progressbar import *
import time
import os
rows, columns = os.popen('stty size', 'r').read().split() #Get console size
console_width=int(columns)
total = 10
progress = ProgressBar()
def test():
'''
//Progress Bar Function, Recording Progress
'''
for i in progress(range(total)):
test2()
def test2():
'''
//Execution function, output result
'''
content="nMask'Blog is http://thief.one"
sys.stdout.write("\r"+content+" "*(console_width-len(content)))
time.sleep(1)
sys.stdout.flush()
test()
More advanced uses can use the progressbar module.
system operation
system information
Get python installation path
What I don't know in the process of learning can be added to me? python learning communication deduction qun, 784758214 There are good learning video tutorials, development tools and e-books in the group. Share with you the current talent needs of python enterprises and how to learn python from zero foundation, and what to learn from distutils.sysconfig import get_python_lib print get_python_lib
Get the current python version
sys.version_info sys.version
Get the current time
c=time.ctime() #Custom Format Output ISOTIMEFORMAT='%Y-%m-%d %X' time.strftime( ISOTIMEFORMAT, time.localtime() )
View System Environment Variables
os.environ["PATH"]
Getting System Disk
os.popen("wmic VOLUME GET Name")
Get the current path (including the current py file name)
os.path.realpath(__file__)
Line terminators used by the current platform
os.linesep
Get terminal size
rows, columns = os.popen('stty size', 'r').read().split()
#After Python 3, os can be used
os.get_termial_size()
Exit procedure
- return: Returns the value of the function and exits the function.
- exit(): Exit directly.
- sys.exit(): Raises a SystemExit exception, and if no error is caught, the python program exits directly; after the exception is caught, additional cleanup can be done.
- sys.exit(0): For normal exit, the others (1-127) are abnormal and can throw abnormal things for capture. (Usually used to exit programs in the main thread)
- os._exit(0): Quit the python program directly and the code will not execute afterwards. (Usually used to exit programs in threads)
Network operation
Domain name resolution to ip
ip= socket.getaddrinfo(domain,'http')[0][4][0
Get server version information
sUrl = 'http://www.163.com' sock = urllib2.urlopen(sUrl) sock.headers.values()
File operation
open function, using wb, rb instead of w, r
with open("test.txt","wr") as w:
w.write("test")
This is compatible with Python 2/3.
Output all file names in a directory
def search(paths):
if os.path.isdir(paths): #If it is a directory
files=os.listdir(paths) #List all files in the directory
for i in files:
i=os.path.join(paths,i) #Constructing File Path
search(i) #recursion
elif os.path.isfile(paths): #If it is a document
print paths #Output file name
File search
import glob print glob.glob(r"E:/*.txt")# returns a list Finding files uses only three matches: "*", "?", "[]"“ ”*” Match 0 or more characters; ” Match a single character. ” [] "Matches characters within a specified range, such as: [0-9] matches numbers.
Find the path to the folder with the specified name
def search(paths,file_name,tag,lists):
if os.path.isdir(paths): #If it is a directory
if file_name==tag: #If the directory name is tag
lists.append(paths) #Add this path to the list
else: #If the directory name is not tag
try:
files_list=os.listdir(paths) #List all files in the directory
for file_name in files_list:
path_new=os.path.join(paths,file_name) #Constructing File Path
search(path_new,file_name,tag,lists) #recursion
except: #Error reporting when encountering a special directory name
pass
elif os.path.isfile(paths): #If it is a document
pass
return lists
Data manipulation
Judging data type
isinstance("123",(int,long,float,complex)
String
String Derivation
a="True" b=a if a=="True" else "False" >>>print b True
format method splicing strings and variables
a="{test} abc {test2}".format(test="123",test2="456")
>>>>print a
123 abc 456
//Or:
a="{},{}".format(1,2)
>>>>>print a
1,2
Remove the number after the decimal point
a=1.21311 b=Int(math.floor(a))
String inversion
>>> a = "codementor" >>> a[::-1]
Change the initial letter of a string to uppercase
info = 'ssfef' print info.capitalize() print info.title()
Returns a string in the middle and fills it with spaces to a new string of length width.
"center string".center(width) #Width is set to the console width, and the output string can be controlled in the middle.
List all the letters
print string.ascii_uppercase all capital letters print string. ascii_lowercase all lowercase letters print string.ascii_letters all letters (including case)
List (list)
List removal
ids = [1,4,3,3,4,2,3,4,5,6,1] ids = list(set(ids))
Judge that the list is empty
a=[] if not a:
List operation
a=[1,2,3] b=[3,4,5] set(a)&set(b) and set(a)|set(b) or set(a)-set(b) wrong
Addition of single list elements
a = ["Code", "mentor", "Python", "Developer"] >>> print " ".join(a) Code mentor Python Developer
Multiple list elements are added separately
list1 = ['a', 'b', 'c', 'd']
list2 = ['p', 'q', 'r', 's']
>>> for x, y in zip(list1,list2):
print x, y
ap
bq
cr
ds
Converting nested lists to single lists
a = [[1, 2], [3, 4], [5, 6]] >>> import itertools >>> list(itertools.chain.from_iterable(a)) [1, 2, 3, 4, 5, 6]
Addition of elements in a list
a=[1,2,3](Number) sum(a)
Generate a-z list of strings
map(chr,range(97,123))
List replication
a=[1,2,3] b=a When operating on b, it will affect the content of a, because sharing a memory pointer, b=a [:] is a separate copy.
List inference
if+else Coordination List Resolution
[i if i >5 else -i for i in range(10)]
Multilayer nested list
a=[[1,2],[3,4]] b=[for j in i for i in a] print b [1,2,3,4]
Generate a generator and call the next method to reduce memory overhead.
a=(i else i+1 for i in b if i==1)
Dictionary derivation
Change key and value positions
dict={"a":1,"b":2}
b={value:key for key value in dict.items()}
Dictionary operation (dict)
Screen out key with duplicate values
list1=self.dict_ip.items()
ddict=defaultdict(list)
for k,v in list1:
ddict[v].append(k)
list2=[(i,ddict[i]) for i in ddict if len(ddict[i])>1]
dict_ns=dict(list2)
Dictionary Sorting (py2)
file_dict={"a":1,"b":2,"c":3}
file_dict_new=sorted(file_dict.iteritems(), key=operator.itemgetter(1),reverse=True) ##Dictionary sorting, reverse=True from high to low, itemgetter(1) means sorting by value, 0 means sorting by key.
Dictionary Value Judgment
b={"a":1}
a=b.get("a","") #If there is no a, return ""
c=a if a else 0 #If a exists, return a, otherwise return 0
Module operation
When importing a module, set properties or methods that allow only imports.
fb.py:
-----------------------
__all__=["a","b"]
a="123"
c="2345"
def b():
print "123"
-----------------------
from fb import *
//Variables defined in all can be imported, a and b() can be imported, c can not. If _all_ is not defined, all can be imported.
Import packages in superior directories
sys.path.append("..")
from spider.spider_ import spider_
Import modules in external directories
The _init_ py file needs to be created in the target directory with arbitrary content.
Adding Module Properties
Sometimes in the source code, we need to write our own name and version information, which can be defined in the way of _name_. a.py: #! -*- coding:utf-8 -*- __author__="nMask"
Then when we import the module a, we can output dir(a).
What I don't know in the process of learning can be added to me? python learning communication deduction qun, 784758214 There are good learning video tutorials, development tools and e-books in the group. Share with you the current talent needs of python enterprises and how to learn python from zero foundation, and what to learn >>> import p >>> print dir(p) ['__author__', '__builtins__', '__doc__', '__file__', '__name__', '__package__'] >>> print p.__author__ nmask
Dynamic loading of all modules in a directory
//Catalog:
---test
----a.py
----b.py
---c.py
c.py Import test All modules below:
for path in ["test"]:
for i in list(set([os.path.splitext(i)[0] for i in os.listdir("./"+path)])):
if i!="__init__" and i!=".DS_Store": ##Eliminate unnecessary documents
import_string = "import path+"."+i+"
exec import_string #Execution string content
Function operation
eval/exec
def test(content):
print content
exec("test('abc')")
Output: abc
Note: Exc function has no return value
def test(content):
return content
print eval("test('abc')")
Output: abc
Note: The eval function has a return value
Decorator function
Output current time decorator
def current_time(aclass):
def wrapper():
print "[Info]NowTimeis:",time.ctime()
return aclass()
return wrapper
itertools iterator
p=product(["a","b","c","d"],repeat=2)
----
[("a","a"),("b","b")......]
reduce function
The result of this execution of the function is passed to the next one.
def test(a,b):
return a+b
reduce(test,range(10))
//Result: From 0 + 1 + 2... + 9
enumerate function
Enter list elements and serial numbers
n=["a","b","c"]
for i,m in enumerate(n):
print(i,m)
Function timeout settings
@ Update in 2017.05.27
Setting the timeout time of a function's execution with signal
import time
import signal
def test(i):
time.sleep(0.999)#Simulate timeout
print "%d within time"%(i)
return i
def fuc_time(time_out):
# This is the function timeout control. Replace the following test function with a function that may have an unknown error deadlock.
def handler(signum, frame):
raise AssertionError
try:
signal.signal(signal.SIGALRM, handler)
signal.alarm(time_out)#time_out is timeout
temp = test(1) #The function settings section returns data normally if it does not time out.
return temp
except AssertionError:
print "%d timeout"%(i)# Error reporting if timeout occurs
if __name__ == '__main__':
for i in range(1,10):
fuc_time(1)
Function error retry
Using retrying Module to Realize Function Error Reporting Function
import random
from retrying import retry
@retry
def have_a_try():
if random.randint(0, 10) != 5:
raise Exception('It's not 5!')
print 'It's 5!'
If we run the have_a_try function, it will not finish until random.randint returns 5, otherwise it will continue to be re-executed. Please search for more usage of this module.
Program operation
@ Update in 2017.05.27
Ctrl+C Exit Procedure
ctrl+c exit program is realized by signal.
What I don't know in the process of learning can be added to me?
python Learning Exchange Button qun，784758214
//There are good learning video tutorials, development tools and e-books in the group.
//Share with you the current talent needs of python enterprises and how to learn python from zero foundation, and what to learn
import signal
import sys
import time
def handler(signal_num,frame):
print "\nYou Pressed Ctrl-C."
sys.exit(signal_num)
signal.signal(signal.SIGINT, handler)
# Normally you can start your own program.
# Here, for demonstration, we do a loop that won't jam the machine.
while 1:
time.sleep(10)
# When you press Ctrl-C, you should output a paragraph and exit.
Program restart
Using os.execl Method to Realize Program Restart
import time
import sys
import os
def restart_program():
python = sys.executable
print "info:",os.execl(python, python, * sys.argv)
#The os.execl method will replace its own process in order to achieve the goal of self-restart.
if __name__ == "__main__":
print 'start...'
print u"3 Seconds later,The program will end...".encode("utf8")
time.sleep(3)
restart_program()
Time wall
@ Create this article on April 19, 2017
@ 2017.04.24 Add eval/exec function
@ 2017.05.27 Increase program operation, function timeout, function error retry
@ 2017.08.24 Add format splicing strings and variable, string derivation