I'm a complete beginner in Python, so there are many things I don't know, but I'm going to start with Hello World and do various things.
If you are familiar with Python and have any suggestions, please do not hesitate to contact us!
I think that the OS is Mac and the Python version is 3 assuming.
Python 2 is already installed on Mac. If you check the version, it will be displayed as follows.
python --version
Python 2.7.10
However, since the development of the 2nd system has already been completed, we will change it to the 3rd system.
I installed it from pkg. https://www.python.org/downloads/ (You can also install via brew)
After installing, let's check the version.
python3 --version
Python 3.5.0
In this state, the 2nd and 3rd systems coexist. However, if you make a mistake, don't delete the second series of Python here.
If you delete it as shown below, it will probably be a big problem. http://docs.python.jp/3/using/mac.html
It is used by Apple and third-party software and should not be edited or deleted.
Hello World It is a display of Hello World, the gateway to the iron plate.
Write the following in an editor and save it as hello.py.
hello.py
print ("Hello World")
Go to the directory where hello.py was saved
python3 hello.py
And run
Hello World
Should be displayed.
Now that Hello World is displayed, I would like to lay the foundation for actually writing the code.
I created and ran hello.py to display Hello World, but other than this, I can do the same with just the command line.
That is interactive mode.
At the terminal
python3
Enter. Then you will see the following display.
Python 3.5.0 (v3.5.0:374f501f4567, Sep 12 2015, 11:00:19)
[GCC 4.2.1 (Apple Inc. build 5666) (dot 3)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>>
If this is in the state of ``` >>> , the interactive mode is started.
Now, type `print ('HELLO')` and enter, you should see HELLO.
>>> print('HELLO')
HELLO
In addition to displaying character strings, you can also perform calculations.
>>> 10+10
20
When to finish
quit()
Although it is a Python variable, it seems to be dynamically typed, so you can use it without predefining types such as strings and numbers.
#Set a variable as a number
num1 = 1
num2 = 2
# 1+2
result = num1+num2
#output
print(result)
#Set a variable as a string
string1 = 'a'
string2 = 'b'
# ab
concat = string1 + string2
#output
print(concat)
Result is
3
ab
A string is recognized as a string by enclosing it in single quotes ' or double quotes " .
The following numeric types are supported. Integer (int) Floating point number Complex
It is used when combining multiple values.
Enclose it in [] and separate the values with , .
In the following example, A, B, C are put in the list called listsample, and all the lists are returned.
(Run in interactive mode)
>>> listsample = ['A','B','C']
>>> listsample
['A', 'B', 'C']
You can also specify the index.
>>> list = ['A','B','C']
>>> list[0]
'A'
It seems that there are no constants in Python.
In general, it seems that things defined by uppercase letters and underscores are treated as constants, such as TEST_VALUE.
Although it is not a constant, there is a definition method that cannot change the element of an object called a tuple.
(Run in interactive mode)
#Definition of tuple
>>> taplesample = (100,200,300)
>>> taplesample
(100, 200, 300)
#When the index is specified, the 0th 100 is displayed.
>>> taplesample[0]
100
#This will result in an error
>>> taplesample[0] = 101
Similarly, if you define 100,200,300 in the list and change the 0th 100 to 101, this can be rewritten.
>>> samplelist = [100,200,300]
>>> samplelist[0] = 101
>>> samplelist
[101, 200, 300]
Comment out a single line with #
In the case of multiple lines, if you enclose three single quotation marks ' or double quotation marks " side by side, multiple lines will be commented out.
print('indicate')
'''
print('Do not show')
print('Do not show')
'''
This time, I even displayed Hello World and manipulated simple values. I will write it as part 2 in the future.
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