%s #String %r ... %d #integer %f #Fixed-point notation %1.5f #Fixed-point notation(,5 is a decimal digit) %e #Exponential notation
print("Number 1=%f,Number 2=%.3f" % (1/3, 1/3)) Number 1=0.333333,Number 2=0.333
Set what to add at the end by putting a value in the argument "end"
print("a", end=",") print("b", end=",") print("c")
>>> tax = 12.5 / 100 >>> price= 100.5 >>> price * tax 12.5625 >>> price + _ 113.0625 >>> round(_,2) 113.06
Python coding style is called ** PEP8 **
・ 4 spaces for indentation ・ Tab prohibited ・ 4 spaces are a good compromise between narrow indentation and wide indentation. -Independence of comment lines. ・ Dockstring -Encoding is UTF-8(default)・ ASCII -Put a space around the operator and after the comma ・ Do not put a space just inside the parentheses
・ Compare until one of the sequences runs out ・ Do not compare the same elements ・ Comparison result of different elements
-What is a class variable? ... ** Memory shared by all ** instances ** -What are instance variables? ** Memory of ** unique ** for each ** instance
The following is an example of a mistake ... Do not use mutable for class variables
Class variables and instance variables
class Sample: c_list = ・ ・ ・ Example of using class variables incorrectly def add_c_list(self,data): self.c_list.append(data) print("Output result:", end=" ") sample1 = Sample() sample1.add_c_list("Data 1") sample2 = Sample() sample2.add_c_list("Data 2") for item_data in sample1.c_list: print(item_data, end=" ") ============================= Output result:Data 1 Data 2
Escape sequence counts with one character Line breaks\n counts as one character
>>>print(range(5)) range(0,5) ・ The range function is iterable. ・ The range function is an object
>>>dir(Module name) #dir is a built-in function. Show all names defined by the module.
・ The generality of data types is high, the problem domain is wider than Awk / Perl, and equal to or better than other languages.
Start the interpreter
>>> python -c command >>> python -m module name >>>
-The power operator is exceptionally evaluated from right to left because it has a higher priority than other operators. -When the type to be calculated is confused(int,float), Integers are converted to floating point
Characteristic of character string
>>> word #Error if you specify an index that is too large IndexError Traceback (most recent call last) <ipython-input-4-47f442646512> in <module> ----> 1 Zen IndexError: string index out of range >>> word[10000:20000] #Slicing out of range is handled well ''
Cancel a newline character that spans multiple lines
print("""\ Usage:thingy[options] -h Display this usage message -H hostname Hostname to connect to """)
Calculator in interactive mode. underscore
The last displayed expression is the variable "_"(Underscore). >>> tax = 12.5/100 >>> price = 100.50 >>> price * tax 12.5625 >>> price + _ 113.0625 >>> round(_,2) 113.006
Enumerated character literals are automatically concatenated >>> 'Py' 'thon' 'Python'
Unpacking the list
>>> list(range(3,6)) #Calls with common individual arguments [3,4,5] >>> args = [3,6] #From here on, a special method >>> list(range(*arg)) # *Unpacked with arg. Just 3,It becomes 6. [3,4,5] # range(3,6)Same as >>>
・ Line 1: A brief summary. Beginning with a capital letter, ending the period. ・ Second line: Blank ・ Third line:
def function name(arg1: 'Description of arg1', arg2: 'Description of arg2', , ,)->'Description of the return value': processing
Example of docstring and function annotation
def my_func(n: 'Start adding from this value', m:'Add up to this value') -> 'Total value from n to m': """A function that returns the sum from n to m""" ret = 0 for i in range(n, m+1): ret += i return ret
Use the list as a queue
>>> from collections import deque >>> queue = deque(["A","B","C"]) #Made a cue >>> queue.append("D") #Add D >>> queue.popleft() #Take out the first >>> queue.pop() #Take out the last >>> queue.pop(idx) #Extract idxth
・ Key: Immutable type -Value: changeable type ・ Confirm and obtain (search) the existence of the key key:in operator -Check and get (search) the existence of the value value:in operator, values() -Confirm the existence of a combination of key key and value value:in operator, items()
Multidimensional list sorting
Comparison operator< <= == != is is not in not in
Supplementary information about conditions
・ Comparison operators in and not in ・ ・ ・ Presence / absence of sequence values ・ Operators is and is not ・ ・ ・ Comparison of objects ・ Boolean operator and and or ・ ・ ・ Short circuit operator ・ Combination of comparisons (multiple conditions) if x<y and x>z
Numerical operator> Comparison operator
Sequence comparison, other type comparison
・ When the two are basically the same sequence and the length of one is short, this shorter one is smaller. -For the dictionary order of character strings, compare by Unicode code point number of each character.
>>> import sys,fibo >>> dir(fibo) -Used to check the name defined by the module.
** For module search, in the case of XX module, XX.py is searched in the following order **
Module search path
1. 1. Search in the built-in module ２．sys.Spam using the list of directories obtained with the path variable.Search for py 2-1. Directory with input scripts ２－２．PYTHONPATH 2-3. Default per installation
-A module is a file -The module file is ".py」
-Packages are folders >>>from package name import module name#With this you don't have to make it short and full name when referencing a module >>>import package name.Module name#This requires a long, full name when referencing the module.[Dot delimited module name]Called.
package implementation example
>>> import sound.effects.echo >>> sound.effects.echo.echofilter()#Loading submodules. The reference is the full name. It's not long! !! >>> from sound.effects import echo >>> echo.echofilter()#The reference can be short! !!
Compiled python file
・ Python.Compiled Python code other than py.You can also run a file called pyc -Since it is an interpreter, it is converted to a binary file line by line. -Compiler converts all at once to binary file
・ "Error" is roughly divided into "syntax error" and "exception". ・"Syntax error"Is called "parse error" or "syntax interpretation error" -"Exception" is "an error that occurs when executing even if the statement or expression is correct"
ZeroDivisionError NameError TypeError KeyboardInterrupt #Keyboard interrupt exception[Ctrl]+[c]
Reference module name shortened
>>>from package name.Submodule name import module name#With this you don't have to make it short and full name when referencing a module >>>import package name.Module name#This requires a long, full name when referencing the module.[Dot delimited module name]Called.
import os #Functions that interact with the operating system import glob #Wildcard search for files import sys #Handle command line arguments import re #Regular expressions import math #Floating point mathematics from struct import * #binary import random #random import collections #list import logging #Log
Command line arguments
>>> import sys >>> print(sys.argv)
random module ・ ・ ・ Random sampling tool
>>> import random >>> random.choice(['apple','banana','lemon']) #choice is selected from the list 'apple' >>> random.sample(range(100),10) #sample extracts the second argument from the first argument without duplication >>> random.random() #Random floating point >>> radom.randrange(6) # range(6)Randomly selected integer from
・ Is it log output?(Program executor)It is possible to distinguish whether it is output as information that you want to convey to -Log types can be divided into levels such as Error and Debug. ・ If you specify the format, unified output is easily possible.
Log priority (lowest priority from left)
Low <-> High DEBUG、INFO、WARNING、ERROR、CRITICAL
Package management with pip
>>>pip install package name#Install the latest version of the package >>>pip install package name==2.6.0 #Install a specific version of the package >>> pip install --upgrade package name#Upgrade to the latest version >>>pip uninstall package name#Uninstall package >>> pip list #Installed confirmation >>> pip freeze #Installed confirmation(Output format is pip install) >>>pip show package name#Detailed display of package version,author,summar,Description hp
>>> deactivate #Virtual environment end
Source code encoding
-Python source code encoding: UTF-8 ・ When you dare to change the encoding, it will be as follows #-*- coding:Encoding name-*-
End of interpreter
ctrl+d >>>exit() >>>quit()
Tab completion and history editing
Exit the activated state
Interactive primary / secondary prompt