# time.perf_counter () function in Python

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The perf_counter () function always returns a floating time value in seconds. Returns the value (in fractions of a second) of the performance counter, that is, the clock with the highest available resolution for measuring short durations. It includes the time elapsed during sleep and is system-wide. The return value breakpoint is undefined, so only the difference between the results of successive calls is allowed. In between, we can use time.sleep () and similarly fuctions.

Code # 1: Understand the use of perf_counter .

```# Python program to show time by perf_counter()
from time import perf_counter

# integer input from user, 2 input in single line
n, m = map(int, input().split())

# Start the stopwatch / counter
t1_start = perf_counter()

for i in range(n):
t = int(input()) # user gave input n times
if t % m == 0:
print(t)

# Stop the stopwatch / counter
t1_stop = perf_counter()

print("Elapsed time:", t1_stop, t1_start)

print("Elapsed time during the whole program in seconds:",
t1_stop-t1_start)

```

Output:

pref_counter_ns ():
It always gives an integer time value in nanoseconds. Similar to perf_counter (), but return time in nanoseconds.

Code # 2: Using perf_counter_ns and how to implement it.

```# Python program to show time by
# perf_counter_ns()
from time import perf_counter_ns

# integer input from user, 2 input in single line
n, m = map(int, input().split())

# Start the stopwatch / counter
t1_start = perf_counter_ns()

for i in range(n):
t = int(input()) # user gave input n times
if t % m == 0:
print(t)

# Stop the stopwatch / counter
t1_stop = perf_counter_ns()

print("Elapsed time:", t1_stop, ’ns’, t1_start, ’ns’)

print("Elapsed time during the whole program in ns after n, m inputs:",
t1_stop-t1_start, ’ns’)

```

Compare both output from the program, since perf_counter () returns in seconds and pers_counter_ns () returns in nanoseconds.

Benefits of perf_counter ():

1. perf_counter () will give you a more accurate value than time.clock () …
2. From Python3.8, the time.clock () function will be removed and perf_counter will be used.
3. We can calculate both float and integer values ​​of time in seconds and nanoseconds.

## Python timers

First, take a look at some of the code examples you’ll be using throughout the tutorial. Later, you will add a Python timer to this code to monitor its performance. You will also see some of the easiest ways to measure the execution time of this example.

### perf counter Python

If you look at Python’s built-in time module, you’ll notice several functions that can measure time:

• monotonic()
• perf_counter()
• process_time()
• time()

Python 3.7 introduced several new functions such as thread_time() as well as nanosecond versions of all of the above functions named with the _ns suffix. For example, perf_counter_ns() is the nanosecond version of perf_counter(). Details of these functions will be discussed later. In the meantime, pay attention to what the perf_counter() documentation says:

Returns the value (in fractional seconds) of the performance counter, that is, the clock with the highest available resolution for measuring a short period of time.

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