3 Version of print To add (),2.7 And the following versions are not used
Output string Use ’' Single or double quotes print(‘helllo’)
string+string Sure ,string+ Numbers don't work , To bring up numbers or str(4)#
Square should use ** . 2**2=4 2^2=0
Remainder %
integer // 9//4=2
There is no need to define types for storing arguments a=4
condition =1
while condition<10:
print(condition)
condition=condition+1
True False As the capital
Ctrl+C End with
Pay attention to : end
A language that values program structure
example_list=[1,1,2,3,4,5,6]//list
for i in example_list:
print(i)
ctrl+[ or ctrl+] Indent
range The iterator automatically generated by the computer should include the header but not the tail
range(1,3) Output [1,2]
range(1,10,2) 1-9 In steps of 2
x=1;y=2;z=3
if x<y:# Results output
print('x<y')
if x<y<z:# Results output
print('x<y<z')
if x<y:
print('x<y')
else:
print('x>y')
if x<y:
print('x<y')
elif:
print('x>y')
else:
print('x>y')
Define the equation , Not running , Call is the test
def wpc():
print('this is a test-')
wpc()# Function call
def wpc(a,b):
c=a+b
print('this is a test-'+str(c))#this is a test-3
print('this is a test-',c)#this is a test- 3
wpc(1,2)# Function call
When you use a function with parameters , You must pass on the reference or you will make a mistake ！
To solve the problem of too long parameters , Need to write in a separate line
def sale_car(price,color='red',brand='camy',is_second_hand='true'):# Default parameters
print('price',price,
'color', color,
'brand', brand,
'is_second_hand', is_second_hand,)
sale_car(1000,'red','camy',True)# Cover
sale_car(13100)
Be careful ： Undefined function parameters are put together , The defined function parameters are placed in a block
def wpc(a,b):
c=a+b
return c
wpc(1,2)# Function call
print(wpc(2,4))# Output of function value
It's usually capitalized
APPLE=100# Global variables
def fun():
global b# Global variables
b=50
a=APPLE# local variable
return a+100
print(APPLE)
print(fun())
print(b)
#print(a) Will report a mistake because a Is a local variable
APPLE=100# Global variables
a=None
def fun():
a=20
return a+100
print(APPLE)
print('a past=',a)#None Because it still refers to the second row of global variables
print(fun())#120
print('a now =',a)#None Because it still refers to the second row of global variables , The difference in fun Local variable in a
sudo pip3 install numpy // install
sudo pip3 uninstall numpy // uninstall
sudo pip3 install -U numpy // upgrade numpy
sudo Yes, upgrade to administrator
Write operations
text = " this is my first test.\n this is next line .\n this is last line"
print(text)
my_file = open('myfile.txt','w')# The first one is the file name , The second is what kind of form
my_file.write(text)# Write something
my_file.close()# Remember to close the file
Additional operations
text = " this is my first test.\n this is next line .\n this is last line"
append_text='\n this is appended file'
print(text)
my_file = open('myfile.txt','a')#a It means to add
my_file.write(append_text)
my_file.close()
Read operations
file=open('myfile.txt','r')# Save file to file in
content=file.read()#content It's the content
print(content)
file=open('myfile.txt','r')
content=file.readline()# Read line by line
second=file.readline()
all=file.readlines()# Read out the remaining one , With list stored Tabular form
print(content,second,all)
Running results
this is my first test.
this is next line .
[' this is last line\n', ' this is appended file']
It's similar to a function , Variables start with uppercase
class Calculator:# Properties and methods
name = 'good calculator'
price =18
def add(self,x,y):#self Is itself this class
print(self.name)
result=x+y
print(result)
def minus(self,x,y):
result = x-y
print(result)
def times(self,x,y):
print(x*y)
def divid(self,x,y):
print(x/y)
calcul =Calculator()# Create a class
calcul.add(5,4)# Method of using class
Class has its own functions , Frequently used
class Calculator:# Properties and methods
name = 'good calculator'
price =18# Common property
def __init__(self,name,price,hight=3,width=4,weight=5):# initialization , When defining, you must input parameters , There are default parameters
self.name=name# Given initialization
self.price=price
self.h=hight
self.w=width
self.we=weight
def add(self,x,y):#self Is itself this class
print(self.name)
result=x+y
print(result)
def minus(self,x,y):
result = x-y
print(result)
def times(self,x,y):
print(x*y)
def divid(self,x,y):
print(x/y)
calcul =Calculator()# Create a class
calcul.add(5,4)# Method of using class
a_input =input('give a number')
print('this number is:',a_input)
What the user enters is a string Type oh ！！
The solution is int(input())
An ordered sequence of numbers
#tupe Tuples list list Are a series of numbers in sequence
a_tuple=(12,3,5,15,6)# Parenthesis , Or remove the brackets
another_tuple=2,4,7,6
a_list=[12,3,4,5]
for content in a_tuple:
print(content)
for content in a_list:
print(content)
#tupe Tuples list list Are a series of numbers in sequence
a_tuple=(12,3,5,15,6)# Parenthesis , Or remove the brackets
another_tuple=2,4,7,6
a_list=[12,3,4,5]
for index in range(len(a_list)):#range(5) Generate 0,1,2,3,4 Value ,len() length
print(index)#0,1,2,3
print(a_list[index])#list Start bit 0
a=[1,2,3,4,1,2,3,4]# list
a.append(0)#.append You can add values
print(a)# Print out the list
a.insert(1,0)# stay 1 Add a 0 It's not a modification
print(a)# Print out the list
a.remove(2)# Remove the first occurrence 2
print(a)# Print out the list
print(a[-1])# From back to front is the first for -1
print(a[0:3])# Print 0,1,2 Is the number
print(a[:3])# Omit 0
print(a[-3:])# Print -3 To the last That is to say -3,-2,-1 position
print(a)
print(a.index(0))# Print first appears 2 The index of index It's worth
print(a.count(1))# The value of print statistics is 1 How many numbers are there ？
a.sort()# Sort from small to large , And cover the original list
print(a)
a.sort(reverse=True)# Sort from big to small , And cover the original list
print(a)
Multidimensional list, More advanced use numpy,pandas
a=[1,2,3,4,5]
mutil_dim_a=[ [1,2,3],
[2,3,4],
[3,4,5]]
print(a[1])# Output sheet list Of the 2 It's worth 2
print(mutil_dim_a[0][1])# Output 2
A list is the output in order , The dictionary is out of order
a_list=[1,2,3,4,5,5,4]
d1={
'apple':1,'pear':2,'orange':3}# Need a pair of key values
d2={
1:'a','c':'d'}
print(d1['apple'])# Output Apple Corresponding value
print(d1)# Output d1 This dictionary
del d1['apple']# Delete d1 Medium 'apple' This key is right
print(d1)# Output d1 This dictionary
d1['apple']=1# Add a key value pair to the dictionary
print(d1)# Output d1 This dictionary
def fun():
print('hello')
d3={
'apple':[1,2,3],# Add... To the dictionary list
'pear': {
'a':1,'b':2 },# Add a dictionary to the dictionary
'orange':fun}# Add functions to the dictionary
print(d3)
print(d3['pear']['a'])# Take something out of the dictionary
The official module
# The first 1 Methods
#import time
#print(time.localtime())
# The first 2 Methods
#import time as t# in the future time Use both t Instead of
#print(t.localtime())
# The first 3 Methods
from time import *# introduce time All functions of
print(localtime())
Own module
import m1
m1.printdata('hello!!')
a=True
while a:
b=input('type')
if b=='1':
# a=False
#break
continue
else:
pass# Don't do anything?
print('still in run')
print('fininsh run')
try:
#file=open('eee','r')# What went wrong , Get into Exception
file=open('eee','r+')# Get into else Error free condition ,r+ It's a read-write operation
except Exception as e:# The error exists e In this variable , Let's proceed to error handling
print('there is no file named eee')# Print error messages
response = input('do you want to create a new file?')
if response=='y':
file=open('eee','w')
else:
pass
else:# If there are no errors, deal with them here
file.write('sss')
file.close()
map It's the function + Parameters ,lambda Is to simplify the function ,zip It's for iterators
zip
a=[1,3,4]
b=[0,7,8,9]
print(zip(a,b))
print(list(zip(a,b)))# Output [(1, 0), (3, 7), (4, 8)]
# The output of the iterator
for i,j in zip(a,b):
print(i/2,j*2)
print(list(zip(a,a,b)))# Can output more things
lambda
def fun1(x,y):
return (x+y)
print(fun1(2,3))
fun2=lambda x,y:x+y# use lambda Define a simple equation
print(fun2(2,3))
map
def fun1(x,y):
return (x+y)
print(fun1(2,3))
fun2=lambda x,y:x+y# use lambda Define a simple equation
print(fun2(2,3))
print(map(fun1,[1],[2]))# Output an object ,map( function , Input parameters )
print(list(map(fun1,[1],[2])))
print(list(map(fun1,[1,3],[2,5])))#[1,3] Express x1,x2,[2,5] Express y1,y2
import copy
a=[1,2,3]
b=a# Point to the same space
print(id(a))# check a The index of
print(id(b))# check b The index of
b[0]=11# change b, Change at the same time a
print(a)
print(id(a)==id(b))# return true
c=copy.copy(a)#copy Shallow copy, The first time it's different , Those after the second floor point to the same space
print(id(a)==id(c))# return false
c[1]=0
print(a)# Don't change
print(c)
d=[1,2,[3,4]]
e=copy.copy(d)
print(id(d)==id(e))# return false
print(id(e[2])==id(d[2]))# But when list set list In the middle of the day , But it appears id identical
d[0]=11
print(e)# Change first
d[2][0]=666
print(e)# change d in list No.1 in , At the same time e
# If you want to be completely copy
f=copy.deepcopy(d)# It won't change at all . The two are completely different
print(id(f[2])==id(d[2]))
Save and extract functions
import pickle
a_dict= {
'da':111,
2:[23,1,4],
'23':{
1:2,'d':'sad'}}# Dictionaries
file=open('pickle_example.pickle','wb')# The suffix of the filename is pickle,wb It's binary
pickle.dump(a_dict,file)# Like a tractor , hold a_dict Pour to file in
file.close()
import pickle
a_dict= {
'da':111,
2:[23,1,4],
'23':{
1:2,'d':'sad'}}# Dictionaries
# file=open('pickle_example.pickle','wb')# The suffix of the filename is pickle,wb It's binary
# pickle.dump(a_dict,file)# Like a tractor , hold a_dict Pour to file in
# file.close()
# The first method
# file= open('pickle_example.pickle','rb')# read
# a_dict1 = pickle.load(file)# Loading files
# file.close()
# The second method
# The problem that the file may be forgotten has not been solved
with open('pickle_example.pickle','rb') as file:# Automatically help you close the file
a_dict1 = pickle.load(file) # Loading files
print(a_dict1)# The content is exactly the same
Help you find a different
char_list = ['a','b','c','c','d','d','d']
print(set(char_list))# result {'d', 'a', 'c', 'b'} Not a dictionary , There is no key value pair
char_list = ['a','b','c','c','d','d','d']
print(set(char_list))# result {'d', 'a', 'c', 'b'} Not a dictionary , There is no key value pair
sentence='Welcome to world!'
print(set(sentence))# result {'d', 'c', ' ', 'w', 'm', '!', 'W', 't', 'o', 'l', 'r', 'e'}
# Distinguish between spaces and case
# Only a single form of list or tuple can be passed , Can't list + list
char_list = ['a','b','c','c','d','d','d']
print(set(char_list))# result {'d', 'a', 'c', 'b'} Not a dictionary , There is no key value pair
sentence='Welcome to world!'
print(set(sentence))# result {'d', 'c', ' ', 'w', 'm', '!', 'W', 't', 'o', 'l', 'r', 'e'}
# Distinguish between spaces and case
# Only a single form of list or tuple can be passed , Can't list + list
unique_char=set(char_list)
unique_char.add('x')# Add something
# unique_char.clear()# eliminate set
unique_char.remove('x')# Delete a specific value , Nothing is wrong
unique_char.discard('z')# Delete value , There is nothing without error
print(unique_char)
char_list = ['a','b','c','c','d','d','d']
print(set(char_list))# result {'d', 'a', 'c', 'b'} Not a dictionary , There is no key value pair
sentence='Welcome to world!'
print(set(sentence))# result {'d', 'c', ' ', 'w', 'm', '!', 'W', 't', 'o', 'l', 'r', 'e'}
# Distinguish between spaces and case
# Only a single form of list or tuple can be passed , Can't list + list
unique_char=set(char_list)
unique_char.add('x')# Add something
# # unique_char.clear()# eliminate set
# unique_char.remove('x')# Delete a specific value , Nothing is wrong
# unique_char.discard('z')# Delete value , There is nothing without error
set1=unique_char
set2={
'a','e','i'}
print(set1.difference(set2))# Output it has he has nothing Output {'d', 'x', 'b', 'c'}
print(set1.intersection(set2))# Output what it has in common
For future reptiles
import re
# matching string
pattern1 = "cat"
pattern2 = "bird"
string = "dog runs to cat"
print(pattern1 in string) # True
print(pattern2 in string) # False
# regular expression
pattern1 = "cat"
pattern2 = "bird"
string = "dog runs to cat"
# It can be seen that , If re.search() Found the result , It will return one match Of object.
# If it doesn't match , It will be returned None. This re.search() It's just re One of the features in
print(re.search(pattern1, string)) # <_sre.SRE_Match object; span=(12, 15), match='cat'>
print(re.search(pattern2, string)) # None
print('\n')
# multiple patterns ("run" or "ran")
ptn = r"r[au]n" # [ There are two situations ], You need to add a r Used to indicate that this is a regular expression , Instead of ordinary strings
print(re.search(ptn, "dog runs to cat")) # <_sre.SRE_Match object; span=(4, 7), match='run'>
# Again , brackets [] It can also be the following or a combination of these .
# such as [A-Z] It means all capital English letters . [0-9a-z] The representation can be a number or any lowercase letter .
print(re.search(r"r[A-Z]n", "dog runs to cat")) # None
print(re.search(r"r[a-z]n", "dog runs to cat")) # <_sre.SRE_Match object; span=(4, 7), match='run'>
print(re.search(r"r[0-9]n", "dog r2ns to cat")) # <_sre.SRE_Match object; span=(4, 7), match='r2n'>
print(re.search(r"r[0-9a-z]n", "dog runs to cat")) # <_sre.SRE_Match object; span=(4, 7), match='run'>
In addition to defining their own rules , There are many matching rules that are defined for you in advance . Here are some special matching types for you to summarize , Then give some examples .
print(re.search(r"r\dn", "run r4n"))
print(re.search(r"r\Dn", "run r4n"))
print(re.search(r"r\sn", "r\nn r4n"))
print(re.search(r"r\Sn", "r\nn r4n"))
print(re.search(r"r\wn", "r\nn r4n"))
print(re.search(r"r\Wn", "r\nn r4n"))
print(re.search(r"\bruns\b", "dog runs to cat"))
print(re.search(r"\B runs \B", "dog runs to cat"))
print(re.search(r"runs\\", "runs\ to me"))
print(re.search(r"r.n", "r[ns to me"))
print(re.search(r"^dog", "dog runs to cat"))
print(re.search(r"cat$", "dog runs to cat"))
print(re.search(r"Mon(day)?", "Monday"))
print(re.search(r"Mon(day)?", "Mon"))
If a string has many lines , We want to use ^ Form to match the characters at the beginning of the line , If it is not successful in the usual form . Like the following “I” Appears at the beginning of the second line , But use r"^I" But it doesn't match the second line , Now , We're going to use Another parameter , Give Way re.search() Each line can be processed separately . This parameter is flags=re.M, Or it can be written like this flags=re.MULTILINE.
string = """ dog runs to cat. I run to dog. """
print(re.search(r"^I", string)) # None
print(re.search(r"^I", string, flags=re.M)) # <_sre.SRE_Match object; span=(18, 19), match='I'>
If we want a rule to be repeated , It can also be implemented in regular , And there are many ways to realize . It can be divided into these three types :
* : Repeat zero or more times + : Repeat one or more times {n, m} : repeat n to m Time {n} : repeat n Time Examples are as follows :
# * : occur 0 or more times
print(re.search(r"ab*", "a"))
print(re.search(r"ab*", "abbbbb"))
# + : occur 1 or more times
print(re.search(r"ab+", "a"))
print(re.search(r"ab+", "abbbbb"))
# {n, m} : occur n to m times
print(re.search(r"ab{2,10}", "a"))
print(re.search(r"ab{2,10}", "abbbbb"))
We can even group what we find , Use () Can easily achieve this . By grouping , We can easily locate what we find . Like here (\d+) In the group , What we need to find is some numbers , stay (.+) In this group , We will find “Date: “ All the rest . When using match.group() when , He will return the contents of all groups , And if you give .group(2) Add a number , It can locate which group of information you need to return .
match = re.search(r"(\d+), Date: (.+)", "ID: 021523, Date: Feb/12/2017")
print(match.group()) # 021523, Date: Feb/12/2017
print(match.group(1)) # 021523
print(match.group(2)) # Date: Feb/12/2017
occasionally , There will be many groups , Using numbers alone may be difficult to find the group you want , Now , If you have a name as an index , It will be a very easy thing . We need to write this form at the beginning of parentheses ?P< name > Just define a name for this group . Then you can use this name to find the content of this group .
match = re.search(r"(?P<id>\d+), Date: (?P<date>.+)", "ID: 021523, Date: Feb/12/2017")
print(match.group('id')) # 021523
print(match.group('date')) # Date: Feb/12/2017
What we said earlier is that we only found the first match , If you need to find all the matches , We can use findall function . And then it goes back to a list . Note that there is a new knowledge point below , | yes or It means , If it weren't for the former, if it weren't for the latter .
# findall
print(re.findall(r"r[ua]n", "run ran ren")) # ['run', 'ran']
# | : or
print(re.findall(r"(run|ran)", "run ran ren")) # ['run', 'ran']
We can also match some forms of strings through regular expressions and then replace them . Use this matching re.sub(), Will compare python Self contained string.replace() Be flexible .
print(re.sub(r"r[au]ns", "catches", "dog runs to cat")) # dog catches to cat
Come again Python There is a string segmentation function in , For example, if you want to get all the words in a sentence . such as "a is b".split(" "), This will produce a list of all the words . But in regular , This ordinary segmentation can also be done incisively and exquisitely .
print(re.split(r"[,;\.]", "a;b,c.d;e")) # ['a', 'b', 'c', 'd', 'e']
Last , We can still use compile After the regular , To reuse this regular . Let's start with regular compile Enter a variable , such as compiled_re, Then use this directly compiled_re To search for .
compiled_re = re.compile(r"r[ua]n")
print(compiled_re.search("dog ran to cat")) # <_sre.SRE_Match object; span=(4, 7), match='ran'>
