Python 实用宝典

Question 1

I have a list in Python e.g.

names = ["Sam", "Peter", "James", "Julian", "Ann"]

I want to print the array in a single line without the normal ” []

names = ["Sam", "Peter", "James", "Julian", "Ann"]
print (names)

Will give the output as;

["Sam", "Peter", "James", "Julian", "Ann"]

That is not the format I want instead I want it to be like this;

Sam, Peter, James, Julian, Ann

Note: It must be in a single row.

Question 2

print(', '.join(names))

This, like it sounds, just takes all the elements of the list and joins them with ', '.

Question 3

Here is a simple one.

names = ["Sam", "Peter", "James", "Julian", "Ann"]
print(*names, sep=", ")

the star unpacks the list and return every element in the list.

Question 4

General solution, works on arrays of non-strings:

>>> print str(names)[1:-1]
'Sam', 'Peter', 'James', 'Julian', 'Ann'

Question 5

If the input array is Integer type then you need to first convert array into string type array and then use join method for joining with , or space whatever you want. e.g:

>>> arr = [1, 2, 4, 3]
>>> print(", " . join(arr))
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: sequence item 0: expected string, int found
>>> sarr = [str(a) for a in arr]
>>> print(", " . join(sarr))
1, 2, 4, 3
>>>

Direct using of join which will join the integer and string will throw error as show above.

Question 6

There are two answers , First is use ‘sep’ setting

>>> print(*names, sep = ', ')

The other is below

>>> print(', '.join(names))

Question 7

This is what you need

", ".join(names)

Question 8

','.join(list) will work only if all the items in the list are strings. If you are looking to convert a list of numbers to a comma separated string. such as a = [1, 2, 3, 4] into '1,2,3,4' then you can either

str(a)[1:-1] # '1, 2, 3, 4'

or

str(a).lstrip('[').rstrip(']') # '1, 2, 3, 4'

although this won’t remove any nested list.

To convert it back to a list

a = '1,2,3,4'
import ast
ast.literal_eval('['+a+']')
#[1, 2, 3, 4]

Question 9

You need to loop through the list and use end=" "to keep it on one line

names = ["Sam", "Peter", "James", "Julian", "Ann"]
    index=0
    for name in names:
        print(names[index], end=", ")
        index += 1

Question 10

print(*names)

this will work in python 3 if you want them to be printed out as space separated. If you need comma or anything else in between go ahead with .join() solution

Question 11

I don’t know if this is efficient as others but simple logic always works:

import sys
name = ["Sam", "Peter", "James", "Julian", "Ann"]
for i in range(0, len(names)):
    sys.stdout.write(names[i])
    if i != len(names)-1:
        sys.stdout.write(", ")

Output:

Sam, Peter, James, Julian, Ann

Question 12

The following function will take in a list and return a string of the lists’ items. This can then be used for logging or printing purposes.

def listToString(inList):
    outString = ''
    if len(inList)==1:
        outString = outString+str(inList[0])
    if len(inList)>1:
        outString = outString+str(inList[0])
        for items in inList[1:]:
            outString = outString+', '+str(items)
    return outString

问题：单行不带括号的打印列表

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