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Introduction to Python Sleep FunctionIn this article, we will see one of the most used functions that are provided by the time module in Python is the sleep() function. The sleep() function of the time module is used to suspend or halt the current code or thread’s execution for the given number of times in seconds. The sleep() function which takes an argument as time in the number of seconds, which can be specified in floating-point for accuracy. This sleep() function is used in applications like dramatic string printing, and this is also used in the multithreading process.
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Working of sleep() Function in PythonIn this section, we will see the Python time method sleep(). The sleep() function suspends the code or thread execution for the specified number of times in seconds in a floating-point number, which can be used to specify the accurate sleep time to the argument. Let us syntax and examples of this function in the below sections.
Syntax:
time.sleep(ts)Parameters:
ts: This parameter is used to specify the time that execution should be suspended in seconds.
sleep(): It will return nothing as it is just used to suspend the function or code or thread for the specified time in seconds.
Examples to Implement sleep() Function in PythonBelow are the examples of sleep() Function in Python:
Example #1Code:
import time print("Simple program to demonstrate sleep function:") print("The Start time is as follows : ") print(time.ctime()) time.sleep( 5 ) print("The End time is as follows:" ) print(time.ctime())Output:
Explanation: In the above program, we can see that firstly we need to import the time module to used the sleep() function as it is the function of a time module in Python. We can see the first start time is displayed using the ctime() function of the time module, which is displays the current time. Then we saw the end time to display using the sleep() function to stop the execution and then display the current time when the function is stopped executing the thread using the sleep() function.
Example #2A dramatic way of printing the given message or String.
Code:
import time print("Program to demonstrate sleep() function used for printing words letter by letter:") strn = "Educba" print("The given word is as follows:") print(strn) for i in range(0, len(strn)): print(strn[i], end ="") time.sleep(0.3)Output:
Explanation: In the above program, we saw that we have a string defined in this program as “Educba”, so we are trying to print the word letter by letter by using the sleep() function. In this, we have the time specified as 0.3 seconds. This means after every 0.3 seconds, each letter is printed using for loop, having the start range as 0 index of the length of the given string up to the end of the length of the given string and sleep function. To see the visual effect, we have to execute the above program in the local Python editor.
Example #3Code:
import time from threading import Thread class Worker(Thread): def run(self): for x in range(0, 12): print(x) time.sleep(1) class Waiter(Thread): def run(self): for x in range(100, 103): print(x) time.sleep(5) print("Starting Worker Thread will start from :") Worker().start() print("Starting Waiter Thread will stop at:") Waiter().start() print("Done")Output:
ConclusionIn this article, we conclude that we have seen the syntax and working of Python’s sleep() function with examples. In this article, we saw from which module this sleep() function can be defined. Therefore we saw we need to import a time module that provides various methods, and the sleep() function is the most popular method of time module in Python. In this article, we saw a simple example of demonstrating the sleep() function with the number of seconds specified as an argument. Lastly, we saw the sleep() function applications, which are used in dramatic printing and in multi-threading.
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Types And Examples Of Python Validation
Introduction to Python Validation
Whenever the user accepts an input, it needs to be checked for validation which checks if the input data is what we are expecting. The validation can be done in two different ways, that is by using a flag variable or by using try or except which the flag variable will be set to false initially and if we can find out that the input data is what we are expecting the flag status can be set to true and find out what can be done next based on the status of the flag whereas while using try or except, a section of code is tried to run. If there is a negative response, then the except block of code is run.
Types of Validation in PythonThere are three types of validation in python, they are:
Type Check: This validation technique in python is used to check the given input data type. For example, int, float, etc.
Length Check: This validation technique in python is used to check the given input string’s length.
Range Check: This validation technique in python is used to check if a given number falls in between the two numbers.
The syntax for validation in Python is given below:
Syntax using the flag:
flagName = False while not flagName: if [Do check here]: flagName = True else: print('error message')The status of the flag is set to false initially, and the same condition is considered for a while loop to make the statement while not true, and the validation is performed setting the flag to true if the validation condition is satisfied; otherwise, the error message is printed.
Syntax using an exception:
while True: try: [run code that might fail here] break except: print('This is the error message if the code fails') print('run the code from here if code is successfully run in the try block of code above')print(‘run the code from here if code is successfully run in the try block of code above)
We set the condition to be true initially and perform the necessary validation by running a block of code, and if the code fails to perform the validation, an exception is raised displaying the error message and a success message is printed if the try block successfully executes the code.
Examples of Python ValidationExamples of python validation are:
Example #1Python program using a flag to validate if the input given by the user is an integer.#Datatype check.
#Declare a variable validInt which is also considered as flag and set it to false validInt = False #Consider the while condition to be true and prompt the user to enter the input while not validInt: #The user is prompted to enter the input age1 = input('Please enter your age ') #The input entered by the user is checked to see if it’s a digit or a number if age1.isdigit(): #The flag is set to true if the if condition is true validInt = True else: print('The input is not a valid number') #This statement is printed if the input entered by the user is a number print('The entered input is a number and that is ' + str(age1))Output:
Example #2Python program uses flag and exception to validate the type of input given by the user and determine if it lies within a given range. #Range Check.
Code:
#Declare a variable areTeenager which is also considered as flag and set it to false areTeenager = False #Consider the while condition to be true and prompt the user to enter the input while not areTeenager: try: #The user is prompted to enter the input age1 = int(input('Please enter your age ')) #The input entered by the user is checked if it lies between the range specified except: print('The age entered by you is not a valid number between 13 and 19') #This statement is printed if the input entered by the user lies between the range of the number specified print('You are a teenager whose age lies between 13 and 19 and the entered age is ' + str(age1))Output:
Example #3Python program using the flag to check the length of the input string. #Length Check.
Code:
#Declare a variable lenstring which is also considered as flag and set it to false lenstring = False #Consider the while condition to be true and prompt the user to enter the input while not lenstring: password1 = input('Please enter a password consisting of five characters ') #The input entered by the user is checked for its length and if it is below five lenstring = True else: print('The number of characters in the entered password is less than five characters') #This statement is printed if the input entered by the user consists of less than five characters print('The entered password is: ' + password1)Output:
Benefits
Validation in python helps to improve the security of code.
It prevents third-party users from mishandling the code accidentally or intentionally.
It can be used to check if the input data type is correct or not.
It can be used to check if there are no invalid values in the given input.
It can be used to check if the given input lies in the range or is it out of range.
It can be used to check if the given input meets the constraints specified on them.
It can be used to check if the given input is consistent or not.
It can be used to check if the given input is valid.
It can be used to check if the given input is complete or incomplete.
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Working And Examples Of Matlab Textscan()
Introduction to Matlab Textscan
Inbuilt function from MATLAB, textscan() perform the operation of reading formatted data from text file or string, converting and writing data to cell array.Textscan() supports initializing reading from any point in a file. Once the user opens the file, textscan() can start reading from any point instructed by the user. The subsequent textscan() continues reading operation the file when the last textscan() operation is left off.
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SyntaxSyntax Description
C = textscan(fileID,formatSpec) This form of the command textscan() is used to read data from an open text file indicated by fileID into a cell array, C.
C = textscan(fileID,formatSpec,N) This form of the command textscan() is used to read data from an open text file indicated by fileID into a cell array, Cfor theformatSpec, N times. In order to read additional,textscan() can be called using the original fileIDagain.
C = textscan(chr,formatSpec) This form of the command textscan() is used to read data from the character vector ‘chr’ and store it in the cell array ‘C.’ While reading data from character vector, each time, recurring calls to textscan()re-initiate the scan from the beginning. A scan can be resumed from the last position on request for a position output.
Textscan()tries to match the data in ‘chr’ to the format given in the form offormatSpec.
C = textscan(chr,formatSpec,f) This form of the command textscan() is used to read dataforformatSpecf times, where f is a positive integer.
This form of the command textscan() is used to read data specifying options in the form of one or more Name, Value pair arguments.
The return value
For a file- value equals to return value of ftell(fileID)
Examples of Matlab TextscanDifferent examples are mentioned below:
Example #1Code:
chr_str = '0.31 3.24 5.67 6.44 9.17';Scan_str = textscan(chr_str,'%f'); celldisp(Scan_str)
Output:
Example #2Code:
C_data0 = textscan(ID_file,’%d %f %f %f’)
Output:
Example #3Code:
chr_str = 'It is;my code';Scan_str = textscan(chr_str,'%s','Delimiter',';','EmptyValue',-Inf); celldisp(Scan_str)
Output:
Working of TextScan()Textscan()is designed to convert numeric fields to a specific output type, following MATLAB rules with respect to the process of overflow, truncation, and the application of NaN, Inf, and -Inf.
For example, the integer NaNis represented as zero in MATLAB. Therefore, if textscan() encounters an empty field associated with an integer format specifier, it returns the empty value as zero and not NaN.
Resuming a Text ScanIf textscan() fails to convert a data field, it does not proceed with the operation reading and returns the fields read before the failure. When reading from a file, the reading operation from the same file can be resumed by calling textscan() again having the same file identifier, filed, as the first input argument. For a string reading operation carried out by the textscan() method, the syntax of the two-output argument enables the user to resume the reading operation from the string at the point where the last reading operation is terminated. The following code talks about the implementation of this operation.
celldisp(lastpart)
Output:
Thetextscan() and textread() Functions exhibit similar functionalities, but they differ from each other in various aspects such as:
The textscan() function ensures better performance than that oftextread() method. Hence it is a better choice in case of reading large files.
With the textscan() function, the reading operation can be started reading from any point in the file. Once the file is open by the user as it is a prerequisite for textscan() that it requires the user to open the file first, then the user can have access to any position in the file to begin the textscan() at the desired point whereas the textread() function has limited feature of supporting reading operation only from the beginning of any file.
Subsequent textscan() operations start reading of the given file at that point where the earliertextscan() operation is left off. But in the case of the textread() function, it always begins from the beginning of the input file irrespective of the status of the reading operation carried out by any of the prior textread() function call.
Textscan()supports more options on the conversion of the data being read.
Textscan()is equipped with more user-configurable options that that of textread() operation.
Additional NoteExample:
3.7-2.1i
Output:
Example:
-4j
Output:
3. It is not recommended to include embedded white space to a complex number. Textscan() understands an embedded white space as a field delimiter.
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How Polyfit Function Work In Numpy With Examples?
Introduction to NumPy polyfit
In python, Numpy polyfit() is a method that fits the data within a polynomial function. That is, it least squares the function polynomial fit. For example, a polynomial p(X) of deg degree fits the coordinate points (X, Y). This function returns a coefficient vector p that lessens the squared error in the deg, deg-1,…0 order. However, a RankWarning is issued by polyfit when the fit of the least-squares is poorly conditioned. This means that, as a result of numerical error, the best fit is not properly defined. The outcome can be enhanced by replacing x with x-mean(x) or minimizing the polynomial degree.
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Syntax and parameters of NumPy polyfitBelow is the syntax of the polyfit method in numpy.
numpy.polyfit( x , y , deg , rcond = None , full = False, w = None, cov = False)Parameters:
x: This parameter is array-like which is of the shape of (M,) size.
y: This parameter is array-like which is of the shape of (M,) or (M, K) size.
– Represents the M sample y-coordinate value of (x[i], y[i]).
Deg: int value which is the fitting polynomial degree.
rcond: float value which is considered as optional.
-This parameter represents the relative condition value of the fit.
– Singular numbers that are less than this relative condition to the highest singular value can be avoided.
-len(x)*ep is the default value of rcond.
-Here, ep is the relative precision of the type float.
-In most cases, 2e-16 is the value.
full: A boolean value which is optional
-This is considered as a switch that is responsible for the nature of value returned.
-If the value is false, it returns the coefficients.
– If the value is true, it returns the diagnostic data from the singular value decomposition.
w: This parameter is array-like which is of the shape of (M,) size.
-This parameter weights to put to the sample point’s y-coordinates.
-In the case of Gaussian uncertainties, 1/sigma has to be used instead of 1/sigma**2
cov: A boolean value which is optional
-This parameter returns the estimate as well as the estimated covariance matrix.
-If the value of full is true, this parameter won’t return.
Return value:
p: This parameter is an ndarray which is of shape ( deg + 1, ) or ( deg + 1,K)
-This is the polynomial coefficient which has the highest power mentioned first.
– If the value of y is 2-dimensional, the kth dataset coefficient will be set as p[:,k].
Moreover, the list [residuals, rank, singular_values, rcond] will be returned only if the value of full is true. Here, residuals are the residual of the least square fit; Rank is the scaled vandermonde coefficient matrix rank, singular value, and the value of rcond.
V: This value is a ndarray which is of shape M, M) or (M, M, K).
– This value will be returned only if the value of full is false and the value of cov is true.
How polyfit function work in NumPy?Now, let us see how to fit the polynomial data with the help of a polyfit function from the numpy standard library, which is available in Python.
Assume that some data is available in the polynomial. This is to use the function polyfit() for fitting the data available in the polynomial.
A polynomial with a degree of 1 is the simplest known polynomial.
It is mentioned using the equation y=m*x+c
Similar to that, the degree 2 quadratic equation is denoted by the equation
Y = ax**2 + bx + cIn this case, the polyfit method will find all the m, c coefficients for degree 1. This will calculate the a, b, and c coefficients for degree 2.
Below is a sample code for a simple line.
Code:
import matplotlib.pyplot as mp import numpy as np x = np.linspace( -10 , 10 , 5 ) y = 2*x + 5 mp.plot( x , y , 'o' )If the function polyfit() is also added, code changes as shown below.
import matplotlib.pyplot as mp import numpy as np x = np.linspace( -10 , 10 , 5 ) y = 2*x + 5 coeff = np.polyfit(x,y,2) xn = np.linspace(-20,20,100) yn = np.poly1d(coeff) mp.plot( xn,yn(xn),x,y,'o')Note:
In some cases, fitting polynomial coefficients is intrinsically badly conditioned. For example, it is during the cases when the polynomial degree is higher or the interval of sample points is poorly centered. Moreover, the quality of the fit has to be always checked in the cases mentioned above. If the polynomial fits are not that satisfactory, a good alternative will be splined.
Examples of NumPy polyfit Example #1Python program to fit a polynomial function
Code:
import numpy as np import matplotlib.pyplot as mp np.random.seed(12) x = np.linspace( 0, 1, 25 ) y = np.cos(x) + 0.3*np.random.rand(25) p = np.poly1d( np.polyfit(x, y, 4) ) t = np.linspace(0, 1, 250) mp.plot(x, y, 'o', t, p(t), '-') mp.show()Output:
In this program, first, import the libraries matplotlib and numpy. Set the values of x, y, p, and t. Then, using the values of this x, y, p, and t, plot the polynomial by fitting it.
Example #2Python program to fit a polynomial function of a simple line
Code:
import numpy as np import matplotlib.pyplot as mp np.random.seed(12) x=np.linspace(-20,20,10) y=2*x+5 coeff = np.polyfit(x,y,2) xn = np.linspace(-20,20,100) yn = np.poly1d(coeff) mp.plot( xn,yn(xn),x,y,'o')Output:
In this program, also, first, import the libraries matplotlib and numpy. Set the values of x and y. Then, calculate the polynomial and set new values of x and y. Once this is done, fit the polynomial using the function polyfit().
ConclusionNumpy polyfit() is a method available in python that fits the data within a polynomial function. Here, it least squares the function polynomial fit. That is, a polynomial p(X) of deg degree is fit to the coordinate points (X, Y). In this article, different aspects such as syntax, working, and examples of polyfit() function are explained in detail.
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Working Of C++ Ofstream With Programming Examples
Introduction to C++ ofstream
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Syntax:
Given below is the syntax of C++ ofstream:
ofstream variable_name; variable_name.open(file_name);
variable_name is the name of the variable.
file_name is the name of the file to be opened.
Working of C++ ofstream
The standard library called iostream which is used to read from the standard input and write to the standard output by providing the methods cin and cout, likewise there is another standard library in C++ called fstream to read the data from the file and to write the data into the file.
The standard library fstream provides three data types namely ofstream, ifstream and fstream.
Ofstream is derived from the class ostream class.
Examples of C++ ofstreamGiven below are the examples mentioned:
Example #1C++ program to demonstrate ofstream in a program to write the data to file and then read the contents from the file.
Code:
using namespace std; int main () { ofstream file1("newfile.dat"); file1 << "The contents written to the file are: Welcome to C++ " << endl; file1.close(); string read1; ifstream file2("newfile.dat"); cout << "The contents in the file are : " << endl; while (getline (file2, read1)) { cout << read1; file2.close(); } }Explanation:
In the above program, the header file fstream is imported to enable us to use ofstream and ifstream in the program. Then another header file iostream is imported to enable us to use cout and cin in the program. Then the standard namespace std is used. Then the file by name newfile is opened using the ofstream data type to write contents into the file.
Then by using the variable of ofstream data type, the contents is written into the file. Then by using the variable of ofstream data type, the file that was opened to write the contents into the file is closed.
Then a string variable is defined. Then the file by name newfile is opened using the ifstream data type to read the contents from the file. Then by using the variable of ifstream data type, the contents is read from the file and display as the output. Then by using the variable of ifstream data type, the file that was opened to read the contents from the file is closed.
Example #2C++ program to demonstrate ofstream in a program to write the data to file and then read the contents from the file.
using namespace std; int main () { ofstream file1("filename.dat"); file1 << "The contents written to the file are: Learning is fun" << endl; file1.close(); string read1; ifstream file2("filename.dat"); cout << "The contents in the file are : " << endl; while (getline (file2, read1)) { cout << read1; file2.close(); } }Output:
Explanation:
In the above program, the header file fstream is imported to enable us to use ofstream and ifstream in the program. Then another header file iostream is imported to enable us to use cout and cin in the program. Then the standard namespace std is used. Then the file by name filename is opened using the ofstream data type to write contents into the file.
Then by using the variable of ofstream data type, the contents is written into the file. Then by using the variable of ofstream data type, the file that was opened to write the contents into the file is closed. Then a string variable is defined. Then the file by name filename is opened using the ifstream data type to read the contents from the file.
Then by using the variable of ifstream data type, the contents is read from the file and display as the output. Then by using the variable of ifstream data type, the file that was opened to read the contents from the file is closed.
Advantages
<< operator is supported by ofstream in C++.
The contents of the file written using ofstream can be flushed automatically using the classes of fstream and the chances of corruption of file is less.
Recommended ArticlesHow Does The Null Function Work In C++ With Examples?
Introduction to C++ null
The null function is used to assign value to the variable; this can be treated as the default value for the variable defined in many programming languages. Null functions can be used to assign value to a pointer that is not pointing to any address and contain any garbage value, so the null function will assign them a special value called ‘NULL’, which means they are now null pointer. In this topic, we are going to learn about C++ null.
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Syntax
This is very simple to assign a null value to the variable in C++; we just need to do this at the time of initialization only. This variable then turns to be treated as the Null pointer. Below see the syntax to understand this better and used while programming see below;
int main () { int *your_ptr_name = NULL; }In the above syntax, we are using the NULL value here to assign to a pointer. First, we have to define the pointer, and then we can initialize it with NULL. Sample practice syntax for more understanding see below;
int main () { int *myptr = NULL; } How does the null function work in C++?As of now, we know that we use Null functions to assign some special value to the pointer variable. By the use of this, we can give them a logical value when they are not pointing to any address in the memory. That’s why it is also known as a special value to the pointer. Also, we know that pointer holds the memory address, so if we want them to point to some other value, in that case, we can use NULL here. But we have to use this while initiation of the pointer. Now we will see one example and understand its working how it actually works; for more detail, see below;
Example:
using namespace std; int main () { int *myptr1 = NULL; int *myptr2= NULL; int *myptr3 = NULL; if(!myptr1) { cout << “demo value for myptr ” << myptr1 ; } return 0; }
In this example, we create three different pointers, and all of them point to the NULL here. So as we can see, we have initialized the value for the variable at the time of declaring the variables. After this, we are making one check here to check and print the value of the pointer. If the statement coming out to be right, then the print statement will be executed; otherwise, it will return. If we see it will assign a default value of ‘0’ to the pointer. So a null can be an integer value as well when it is not pointing to the memory address. In the if statement above, as you can see pointer is pointing to null, but here it got converted into Boolean false, and if the value for any of the pointers is not null, then it will convert into Boolean true.
So in this way, we can test our pointers as well. Null functions are nothing but a way to assign value to the pointer variable in c++. We can also do dereferencing of our null pointers in c++, but this will lead to unusual behavior of the program. this is because dereferencing means go back to the previous state where it is pointing to before initiation, but if we try to do this in our code, a null pointer still points nowhere because it has no memory address attached with it.
Points to be remembered while working with the NULL functions in c++ see below;
2) If the pointer does not point to any memory address in C++, it does not point to null; we will use NULL functions to assign them value.
3) If we assign a value to a pointer using null functions, then they will convert to Boolean true or false depending on the value they are holding. This is because the null pointer can be integer also.
Examples of C++ nullGiven below are the examples of C++ null:
Example #1In this example, we will see how to initialize the null value to the pointer using the NULL function in C++; this is nothing but the special value we can assign at the time of initialization. There is no particular syntax to do this.
Code:
using namespace std; int main () { cout<<“Demo for null functions in c++”; cout<<“n”; int *myptr1 = NULL; int *myptr2= NULL; int *myptr3 = NULL; cout << “value of the first variabel is::: ” << myptr1 ; cout<<“n”; cout << “value of the second variabel is::: ” << myptr2 ; cout<<“n”; cout << “value of the third variabel is::: ” << myptr3 ; return 0; }
Output:
Example #2In this example, we are going to see how to make a conditional statement while using a NULL pointer in your program and how they change the value while checking them. After the statement, we are assigning them a new value to the point.
Code:
using namespace std; int main () { int var1 =20; int var2 =30; int var3 =40; cout<<“Demo for null functions in c++”; cout<<“n”; int *myptr1 = NULL; int *myptr2= NULL; int *myptr3 = NULL; cout<<“Value before null functions :::”; cout<<“n”; cout << “value of the first variable is before ::: ” << myptr1 ; cout<<“n”; cout << “value of the second variable is before :::” << myptr2 ; cout<<“n”; cout << “value of the third variable is before :::” << myptr3 ; if(!myptr1){ myptr1 = &var1; cout << “value after initialization is ::” ; cout<<“n”; cout << “value of the first variable is after ::: ” << myptr1 ; cout<<“n”; } if(!myptr2){ myptr2 = &var2; cout << “value after initialization is ::” ; cout<<“n”; cout << “value of the second variable is after ::: ” << myptr2 ; cout<<“n”; } if(!myptr3){ myptr3 = &var3; cout << “value after initialization is ::” ; cout<<“n”; cout << “value of the third variable is after ::: ” << 3 ; cout<<“n”; } return 0; }
Output:
ConclusionHence we can use null functions to assign value to the variable; null values are important when our pointer is not pointing to any memory address to avoid the unusual behavior while programming, so null functions or null assigning to a pointer is used to assign a default value when they are not pointing anywhere in the memory address.
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