A nice line of Python code

Public account: You and the cabin by: Peter Editor: Peter

Hello, I’m Peter

Python is known for its syntax brevity. As we’ve learned Python, we’ve always found that Python can help us solve a lot of problems very easily.

Sometimes seemingly complex tasks can be done with even a single line of Python code.

Here is Peter’s introduction to 40 interesting and useful Python code lines. Let’s see how Python can be powerful

Print hello python

Everyone starts with the print function

print("hello python")  
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hello python
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print("hello Peter")  
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hello Peter
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print("Data analyst")  
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Data analystCopy the code

Binary to decimal

int("01110".2)  # 2 ^ 3 ^ 2 + 2 + 2
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14
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Convert octal to decimal

int("140".8)  
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96
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Conversion from hexadecimal to decimal

int("ac1".16)
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2753
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Generates a list of consecutive values

list(range(9))
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[0, 1, 2, 3, 4, 5, 6, 7, 8]
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Gauss sum

One line of code to solve the Gauss sum: Solve for the sum of all numbers from 1 to 100

sum(range(1.101))  The # range function does not contain 101
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5050
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Find the sum of odd and even numbers

# divided by 2 has a remainder of 0 which is even

sum(i for i in range(1.101) if i % 2= =0)  
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2550
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# divided by 2 without a remainder of 0 is odd

sum(i for i in range(1.101) if i % 2! =0)  
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2500
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factorial

import math  Need to use a third party library

math.factorial(6) # 6 * 5 * 4 * 3 * 2 * 1
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720
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Matrix transpose

Matrix transpose is the transformation of rows and columns of a matrix

list1 = [[1.4.7], [2.5.8], [3.6.9]]  Define a nested list
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list(list(x) for x in zip(*list1))  # list function implementation
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[2, 3], [4, 5, 6], [7, 8, 9]]Copy the code

[list(x) for x in zip(*list1)]   # [] symbol implementation
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[2, 3], [4, 5, 6], [7, 8, 9]]Copy the code

for x in zip(*list1):
    print(list(x))
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[1, 2, 3]
[4, 5, 6]
[7, 8, 9]
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Nested list merge

Combine multiple lists into one large list

list4 = [[1.2.3], [4.5.6], [7.8.9]]  Define a list

list(item for list5 in list4 for item in list5) # From big to small
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[1, 2, 3, 4, 5, 6, 7, 8, 9]
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List of merger

a = [1.2.3]
b = [4.5.6]

a.extend(b)
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a
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[1, 2, 3, 4, 5, 6]
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A list of reverse

list6 = [1.2.3.4.5.6.7]

list6[::-1]
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[7, 6, 5, 4, 3, 2, 1]
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The list of unpacked

h,*i,j = [1.2.3.4.5]

print(h)
print(i)
print(j)
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1
[2, 3, 4]
5
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List to heavy

By turning a list into a set, we can take advantage of the de-weighting property of a set and then turn it into a list

list7 = [1.2.3.4.3.2.3.3]

list(set(list7))
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[1, 2, 3, 4]
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A list of filters

The filter function takes two arguments:

• Specify a function
• Iterable objects to be executed, each of which performs the previous function

list(filter(lambda x:x % 3= =0[1.3.6.7.9.10]))  # Find multiples of 3
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[3, 6, 9]
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List derivation

[number for number in range(0.11)]  # []
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[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
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Set derivation

{number for number in range(0.11)}  # {}
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{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10}
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Merge collection

s1 = {1.2.3}
s2 = {4.5.6}

s1.update(s2)
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s1
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{1, 2, 3, 4, 5, 6}
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Dictionary derivation

{i:i**3 for i in range(0.5)}  # I **3 means I to the third power
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{0: 0, 1: 1, 2: 8, 3: 27, 4: 64}
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Merge the dictionary

d1 = {"name1":"xiaoming"."age1": 19}
d2 = {"name2":"xiaoming"."age2": 28}

d1.update(d2)
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d1
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{'name1': 'xiaoming', 'age1': 19, 'name2': 'xiaoming', 'age2': 28}
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if-for

# Find multiples of 3

[number for number in range(0.20) if number % 3= =0] 
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[0, 3, 6, 9, 12, 15, 18]
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if-else

print("Even") if 8 % 2= =0 else ("Odd")
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An even numberCopy the code

print("Even") if 9 % 2= =0 else print("Odd")
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An odd numberCopy the code

Quick sort

list2 = [9.5.1.6.2.8]  Define a list

sorted(list2) # default ascending order
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[1, 2, 5, 6, 8, 9]
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sorted(list2, reverse=True) # descending
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[9, 8, 6, 5, 2, 1]
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list3 = ["ac"."ab"."bb"."aa"."bc"."cd"."ca"]
sorted(list3)
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['aa', 'ab', 'ac', 'bb', 'bc', 'ca', 'cd']
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First we sort by the ASCII value of the first letter, which is ascending by default. A minimum. When the first letter is the same, sort by the second letter

The string is converted to bytes

"string to bytes".encode()
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b'string to bytes'
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Get 26 alphabets

import string

string.ascii_letters  # case
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'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ'
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Get uppercase alphabet

string.ascii_uppercase
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'ABCDEFGHIJKLMNOPQRSTUVWXYZ'
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Get lowercase alphabet

string.ascii_lowercase
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'abcdefghijklmnopqrstuvwxyz'
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String case conversion

"Hello! My name is Peter".lower()   # convert to lowercase
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'hello! my name is peter'
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Another way to write # to lowercase

"Hello! My name is Peter".casefold()  
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'hello! my name is peter'
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"Hello! My name is Peter".upper()  # convert to all uppercase
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'HELLO! MY NAME IS PETER'
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"Hello! My name is Peter".title()  # capitalize
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'Hello! My Name Is Peter'
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Finding the longest string

list7 = ["c"."html"."javascript"."java"]

max(list7, key=len)  The # key argument specifies the function
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'javascript'
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max(list7)  # the default
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'javascript'
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Deletes a number from a string

"".join(list(filter(lambda x: x.isalpha(), "abcde12hk18")))
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'abcdehk'
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list(filter(lambda x: x.isalpha(), "abcde12hk18"))
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['a', 'b', 'c', 'd', 'e', 'h', 'k']
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Strings in lists become numeric values

list(map(int["10"."90"."50"]))
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[10, 90, 50]
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String inversion

"python"[: : -1]
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'nohtyp'
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Switching variable

a, b = 5.8  # Define two variables
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print("Pre-exchange A :",a)
print("Pre-exchange B :",b)
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A: 5 before exchange B: 8 before exchangeCopy the code

a, b = b, a  # Exchange one line of code
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print("After the exchange A :",a)
print("After exchange B :",b)
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After the exchange, A: 8 b: 5Copy the code

Data type checking

isinstance(5.int)  # numerical
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True
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isinstance("python".int)
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False
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isinstance("python".str)  # string
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True
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isinstance([1.3.6].list)  # list
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True
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Fibonacci numbers

fibo = lambda x: x if x <= 1 else fibo(x-1) + fibo(x-2) 

fibo(10)
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55
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Word frequency statistics

Counts the number of single characters in a string

"javascript".count("a")
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2
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"javascript".count("s")
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1
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"hello".count("l")
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2
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Count the number of list elements

import pandas as pd

list10 = [1.3.4.6.1.2.3.1.1.2.5.6.2]

pd.value_counts(list10)
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1    4
2    3
3    2
6    2
4    1
5    1
dtype: int64
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Count the number of string elements

from collections import Counter

Counter("abcdeabcdabcaba")
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Counter({'a': 5, 'b': 4, 'c': 3, 'd': 2, 'e': 1})
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Most statistical element

list10 = [1.3.4.6.1.2.3.1.1.2.4.6.2]

max(list10, key=list10.count)  # element 1 at most
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1
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min(list10, key=list10.count)  Element 3 is the fewest, appearing only once
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3
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The current time

import time

time.time()   # timestamp form
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1632501677.992713
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time.ctime()  # Standard form
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'Sat Sep 25 00:41:18 2021'
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