Pythonic 打印列表项的方法

Question

I would like to know if there is a better way to print all objects in a Python list than this :

myList = [Person("Foo"), Person("Bar")]
print("\n".join(map(str, myList)))
Foo
Bar

I read this way is not really good :

myList = [Person("Foo"), Person("Bar")]
for p in myList:
    print(p)

Isn't there something like :

print(p) for p in myList

If not, my question is... why ? If we can do this kind of stuff with comprehensive lists, why not as a simple statement outside a list ?

Answer 1

Assuming you are using Python 3.x:

print(*myList, sep='\n')

You can get the same behavior on Python 2.x using from __future__ import print_function , as noted by mgilson in comments.

With the print statement on Python 2.x you will need iteration of some kind, regarding your question about print(p) for p in myList not working, you can just use the following which does the same thing and is still one line:

for p in myList: print p

For a solution that uses '\n'.join() , I prefer list comprehensions and generators over map() so I would probably use the following:

print '\n'.join(str(p) for p in myList) 

Answer 2

I use this all the time :

#!/usr/bin/python

l = [1,2,3,7] 
print "".join([str(x) for x in l])

Answer 3

[print(a) for a in list]将在最后给出一堆 None 类型，尽管它会打印出所有项目

Answer 4

For Python 2.*:

If you overload the function __str__() for your Person class, you can omit the part with map(str, ...). Another way for this is creating a function, just like you wrote:

def write_list(lst):
    for item in lst:
        print str(item) 

...

write_list(MyList)

There is in Python 3.* the argument sep for the print() function. Take a look at documentation.

Answer 5

Expanding @lucasg's answer (inspired by the comment it received):

To get a formatted list output, you can do something along these lines:

l = [1,2,5]
print ", ".join('%02d'%x for x in l)

01, 02, 05

Now the ", " provides the separator (only between items, not at the end) and the formatting string '02d' combined with %x gives a formatted string for each item x - in this case, formatted as an integer with two digits, left-filled with zeros.

Answer 6

To display each content, I use:

mylist = ['foo', 'bar']
indexval = 0
for i in range(len(mylist)):     
    print(mylist[indexval])
    indexval += 1

Example of using in a function:

def showAll(listname, startat):
   indexval = startat
   try:
      for i in range(len(mylist)):
         print(mylist[indexval])
         indexval = indexval + 1
   except IndexError:
      print('That index value you gave is out of range.')

Hope I helped.

Answer 7

I think this is the most convenient if you just want to see the content in the list:

myList = ['foo', 'bar']
print('myList is %s' % str(myList))

Simple, easy to read and can be used together with format string.

Answer 8

I recently made a password generator and although I'm VERY NEW to python, I whipped this up as a way to display all items in a list (with small edits to fit your needs...

    x = 0
    up = 0
    passwordText = ""
    password = []
    userInput = int(input("Enter how many characters you want your password to be: "))
    print("\n\n\n") # spacing

    while x <= (userInput - 1): #loops as many times as the user inputs above
            password.extend([choice(groups.characters)]) #adds random character from groups file that has all lower/uppercase letters and all numbers
            x = x+1 #adds 1 to x w/o using x ++1 as I get many errors w/ that
            passwordText = passwordText + password[up]
            up = up+1 # same as x increase


    print(passwordText)

Like I said, IM VERY NEW to Python and I'm sure this is way to clunky for a expert, but I'm just here for another example

Answer 9

Assuming you are fine with your list being printed [1,2,3], then an easy way in Python3 is:

mylist=[1,2,3,'lorem','ipsum','dolor','sit','amet']

print(f"There are {len(mylist):d} items in this lorem list: {str(mylist):s}")

Running this produces the following output:

There are 8 items in this lorem list: [1, 2, 3, 'lorem', 'ipsum', 'dolor', 'sit', 'amet']

Answer 10

OP's question is: does something like following exists, if not then why

print(p) for p in myList # doesn't work, OP's intuition

answer is, it does exist which is:

[p for p in myList] #works perfectly

Basically, use [] for list comprehension and get rid of print to avoiding printing None . To see why print prints None see this

Answer 11

使用单行代码打印给定列表的每个元素

 for i in result: print(i)

Answer 12

You can also make use of the len() function and identify the length of the list to print the elements as shown in the below example:

sample_list = ['Python', 'is', 'Easy']

for i in range(0, len(sample_list)):

      print(sample_list[i])

Reference : https://favtutor.com/blogs/print-list-python

Answer 13

you can try doing this: this will also print it as a string

print(''.join([p for p in myList]))

or if you want to a make it print a newline every time it prints something

print(''.join([p+'\n' for p in myList]))