Python увеличение числа на единицу

Python Increment By 1

How do you increase a variable by one in Python? In other popular programming languages to increment a variable by one you can use the simple increment syntax of ++ , for example i++ will make the value of i increase by 1 , but how do you do this in Python?

To increment a variable in Python use the syntax += 1 , for example to increment the variable i by 1 write i += 1 . This is the shorter version of the longer form syntax i = i + 1 .

Here is an example of increasing a variable properly using Python with the += 1 syntax as shown here:

Using ++ In Python

If you try to write i++ syntax in your Python code you will get a SyntaxError as shown below:

>>> def increment_me(i): . print(i++) . File "", line 2 print(i++) ^ SyntaxError: invalid syntax

Therefore, you cannot use this operation ( ++ ) which is found in other popular languages (such as Javascript) to increment an integer variable in Python.

Increase i By More Than 1

If you want to increase the value of the step in Python you can run the syntax multiple times, or just change the constant to reflect the size of the increase for the variable.

For example, if you want to increase the size of the variable i by 2 you can write i += 2 , which will have the following effect:

Increase By Variable

Besides increasing a variable by a constant number you could also swap out the increasing amount by using a variable.

Here’s a simple demonstration showing what would happen if instead of having the constant 1 as the incrementing amount you have the incrementing amount refer to another variable:

>>> a = 3 >>> i = 50 >>> i += a >>> print(i) 53 >>> a = 10 >>> print(i) 53 >>> i += a >>> print(i) 63

You’re also not just limited to constants and variables, you can also use statements, such as the handy one-line if statement , as shown here:

>>> i = 3 >>> i += 1 if True else 2 >>> print(i) 4

As the condition of the if statement above is True the first value of 1 is used when this statement is resolved. Therefore, the outcome of the if statement is 3 + 1 being 4.

Decrement A Variable By 1

Similar to how you increment a variable by one using the syntax += 1 to decrement a variable by one, switch the + symbol with the — symbol so that the syntax now looks like so: -= 1 for example i -= 1 .

Using the same principle of modifying the constant, you could also decrement the variable by applying a negative number instead of a positive number , as seen in this example:

The equivalent of the above operation is to use the same syntax but to use -= instead.

For example, to reduce a variable by an amount, such as 1 , you would use the following operation:

Concatenating Lists & Strings

Besides increasing a numeric variable the same shorthand syntax can also be applied to appending additional items to lists, or for concatenating strings.

Here are some additional use cases where the operation is performed on other data types:

It’s important to note that to append lists together into one both must be of list data type . The following produces a TypeError :

>>> i = [1] >>> i += 2 Traceback (most recent call last): File "", line 1, in TypeError: 'int' object is not iterable

It also doesn’t work if the variable is declared first as an int and a list data type is appended next, as shown:

>>> i = 1 >>> i += [2] Traceback (most recent call last): File "", line 1, in TypeError: unsupported operand type(s) for +=: 'int' and 'list'

The same also applies to strings, the only way the operation works is if both types are of type str , as shown here:

>>> i = 'hello' >>> i += ' world' >>> print(i) 'hello world'

Prepend Lists With += Syntax & List Comprehensions

You can also prepend lists using the += syntax on variables that are of a data type combined together with list comprehensions , as shown in this example here:

>>> i = [1, 2, 9] >>> i += [x for x in range(100, 500, 100)] >>> print(i) [1, 2, 9, 100, 200, 300, 400]

SyntaxError When Declaring Data Type

Be mindful you cannot declare the type when using these types of operations in Python 3, otherwise a SyntaxError is thrown, as shown in this example:

>>> i: int = 0 >>> i: int += 1 File "", line 1 i: int += 1 ^ SyntaxError: invalid syntax

To remove the SyntaxError just remove the type declaration after the variable as shown in this example:

Summary

Does i++ work in Python? No, it doesn’t. It will return a SyntaxError . Therefore, to achieve the same purpose of incrementing a variable, i , by 1 using the syntax i += 1 or its longer form syntactical representation i = i + 1 .

The syntax += is quite useful in not only being able to increase a variable by an amount but also has further utility in being able to concatenate strings and lists provided the original data type of the variable being operated on is a string or list respectively.

You might want to see an application for incrementing a variable by 1 and how it is used when creating an incrementing file name in Python .

Primary Sidebar

Hello! My name is Ryan Sheehy the author of ScriptEverything.com

This website acts as a second brain of sorts for all the hacks and explorations I find when trying to solve problems at work.

Footer

Spreadsheets

I have been using spreadsheets since as early as 1996 and I continue to use this great productivity tool on a daily basis.

Python Code

I have been using Python since the late 1990’s due to the limitations of Excel’s VBA. I enjoy being able to wrangle and fetch data externally using Python.

Apps

Sometimes I play, hack and tinker with other applications to scratch an itch.

Copyright © 2023 ScriptEverything.com

Источник

Increment and Decrement operators in Python

Let us understand Increment and Decrement operators in Python.

Python does not allow using the “(++ and –)” operators. To increment or decrement a variable in python we can simply reassign it. So, the “++” and “–” symbols do not exist in Python.

Python increment operator

Now, let us understand about Python increment operator using an example.

In python, if you want to increment a variable we can use “+=” or we can simply reassign it “x=x+1” to increment a variable value by 1.

After writing the above code (python increment operators), Ones you will print “x” then the output will appear as a “ 21 ”. Here, the value of “x” is incremented by “1”.

You can refer to the below screenshot for increment operator in python.

In the below code, we will see another example to increment the variable using “+=”, which does the same.

After writing the above code, Ones you will print “x” then the output will appear as a “ 22 ”. Here, the value of “x” is incremented by “1”.

You can refer to the below screenshot.

Python decrement operator

Let us understand now, Python decrement operator with an example.

To decrement a variable in python we can use “-=” or “x=x-1” operators in python to reduce the value of a variable by 1.

After writing the above code (python decrement operators), Ones you will print “x” then the output will appear as a “ 20 ”. Here, the value of “x” is decremented by “1”.

You can refer to the below screenshot for decrement operator in python.

In the below code, we will see another example to decrement the variable using “-=”, which does the same.

After writing the above code, Ones you will print “x” then the output will appear as a “ 19 ”. Here, the value of “x” is reduced by “1”.

You can refer to the below screenshot.

Increment variable in loop python

Let us see how to increment variable in loop in Python.

In python, to increment a variable value in a loop, we can use the while loop directly for increasing or decreasing the iteration value.

my_list = [11, 12, 13, 14, 15] i = 0 while(i < len(my_list)): print(my_list[i]) i += 2

After writing the above code (increment variable in loop python), Ones you will print “my_list[i]” then the output will appear as an “ 11 13 15 ”. Here, the value is incremented by 2 in every iteration.

You can refer to the below screenshot for increment variable in loop python.

In the below code, we will see another example of the increment variable in loop python by using the range function, as the third parameter of this function will specify the step to increment its index value.

my_list = [11, 12, 13, 14, 15] for i in range(0, len(my_list), 2) print(my_list[i])

• After writing the above code (increment variable in loop python), Ones you will print “my_list[i]” then the output will appear as an “ 11 13 15 ”.
• Here, the range function is used to return the sequence of numbers, were starting from “0”, and specifying the position to stop, also specifying the incrementation by 2.

You can refer to the below screenshot for increment variable in loop python.

How to increment a character in python

How to increment a character in python? It will give an error if you try to increment a character with integer value in Python.

After writing the above code (how to increment a character in python), Ones you will print “a” then the error will appear as a “ TypeError: can only concatenate str (not “int”) to str ”.

You can refer to the below screenshot.

To solve the above typeerror, we will be using ord() and chr() in order to avoid an error. The ord() returns the corresponding ASCII value of character and after adding the integer to it, chr() again converts it into character.

char = ord("N") val = char + 2 increment = chr(val) print(increment)

After writing the above code (how to increment a character in python), Ones you will print “increment” then the output will appear as a “ P “. Here, the “chr” returns the incremented character.

You can refer to the below screenshot how to increment a character in python.

Decrement operators in python for loop

To decrement the index value inside the for loop in Python, we can use the range function as the third parameter of this function will be negative. By making the step value negative it is possible to decrement the loop counter.

for i in range(6, 0, -2): print(i)

• After writing the above code (decrement operators in python for loop), Ones you will print “i” then the output will appear as a “ 6 4 2 ”.
• Here, the range function is used to return the sequence of numbers, here starting from “6”, and it goes on decrementing till 0 positions, also specifying the step to decrement by -2.

You can refer to the below screenshot for decrement operators in python for loop.

Increment operators in python for loop

To increment the operator in loop python we will use the range function, as the third parameter of this function will specify the step to increment its index value.

for i in range(0, 6, 1) print(i)

• After writing the above code (increment operators in python for loop), Ones you will print “i” then the output will appear as an “ 0 1 2 3 4 5 ”.
• Here, the range function is used to return the sequence of numbers, were starting from “0”, and the specified range to stop is 6, also the step to increment is 1.

You can refer to the below screenshot for increment operators in python for loop.

You may like the following Python tutorials:

In this Python tutorial, we learned about Python increment and decrement operators. Also, We covered these below topics as:

• Increment and Decrement operators in Python
• Python increment operator
• Python Decrement operator
• Increment variable in loop python
• How to increment a character in python
• Decrement operators in python for loop
• Increment operators in python for loop

I am Bijay Kumar, a Microsoft MVP in SharePoint. Apart from SharePoint, I started working on Python, Machine learning, and artificial intelligence for the last 5 years. During this time I got expertise in various Python libraries also like Tkinter, Pandas, NumPy, Turtle, Django, Matplotlib, Tensorflow, Scipy, Scikit-Learn, etc… for various clients in the United States, Canada, the United Kingdom, Australia, New Zealand, etc. Check out my profile.

Источник