好程式設計師Python學習路線分享用pprint代替print

阿新 • • 發佈：2019-10-09

好程式設計師Python學習路線分享用pprint代替print更友好的列印除錯資訊
pprint 是 “pretty printer” 的簡寫，“pretty” 的含義是 “漂亮的、美觀的”，因此 pprint 的含義便是：漂亮的列印。

這是個相當簡單卻有用的模組，主要用於列印複雜的資料結構物件，例如多層巢狀的列表、元組和字典等。

先看看 print() 列印的一個例子：

mylist = ["Beautiful is better than ugly.", "Explicit is better than implicit.", "Simple is better than complex.", "Complex is better than complicated."]

print(mylist)

['Beautiful is better than ugly.', 'Explicit is better than implicit.', 'Simple is better than complex.', 'Complex is better than complicated.']

這是一個簡單的例子，全部列印在一行裡。如果物件中的元素是多層巢狀的內容（例如複雜的字典資料），再打印出那肯定是一團糟的，不好閱讀。

使用 pprint 模組的 pprint() 替代 print()，可以解決如下痛點：

設定合適的行寬度，作適當的換行
設定列印的縮排、層級，進行格式化列印
判斷物件中是否有無限迴圈，並優化列印內容

基本使用

pprint(object, stream=None, indent=1, width=80, depth=None, *,compact=False)

預設的行寬度引數為 80，當列印的字元小於 80 時，pprint() 基本上等同於內建函式 print()，當字元超出時，它會作美化，進行格式化輸出。

import pprint

mylist = ["Beautiful is better than ugly.", "Explicit is better than implicit.", "Simple is better than complex.", "Complex is better than complicated."]

pprint.pprint(mylist)

# 超出80字元，列印的元素是換行的
['Beautiful is better than ugly.',
 'Explicit is better than implicit.',
 'Simple is better than complex.',
 'Complex is better than complicated.']

設定縮排

pprint.pprint(mylist, indent=4)

[   'Beautiful is better than ugly.',
    'Explicit is better than implicit.',
    'Simple is better than complex.',
    'Complex is better than complicated.']

設定列印行寬

mydict = {'students': [{'name':'Tom', 'age': 18},{'name':'Jerry', 'age': 19}]}

pprint.pprint(mydict)

# 正常列印
{'students': [{'age': 18, 'name': 'Tom'}, {'age': 19, 'name': 'Jerry'}]}

pprint.pprint(mydict, width=20)

# 行寬為 20
{'students': [{'age': 18,
               'name': 'Tom'},
              {'age': 19,
               'name': 'Jerry'}]}

pprint.pprint(mydict, width=70)

# 行寬為 70
{'students': [{'age': 18, 'name': 'Tom'},
              {'age': 19, 'name': 'Jerry'}]}

設定列印層級

newlist = [1, [2, [3, [4, [5]]]]]

pprint.pprint(newlist, depth=3)

# 超出的層級會用 ... 表示
[1, [2, [3, [...]]]]

用 pprint 替換 print

import pprint
print = pprint.pprint

mylist = ["Beautiful is better than ugly.", "Explicit is better than implicit.", "Simple is better than complex.", "Complex is better than complicated."]

print(mylist)

['Beautiful is better than ugly.',
 'Explicit is better than implicit.',
 'Simple is better than complex.',
 'Complex is better than complicated.']

更多用法請檢視官方文件
總體而言，pprint() 是 print() 的輕量級替代，簡單實用，非常方便，而且還