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初學(xué)Python常見異常錯(cuò)誤，總有一處你會(huì)遇到！
初學(xué)Python常見錯(cuò)誤
- 忘記寫冒號(hào)
- 誤用=
- 錯(cuò)誤 縮緊
- 變量沒有定義
- 中英文輸入法導(dǎo)致的錯(cuò)誤
- 不同數(shù)據(jù)類型的拼接
- 索引位置問題
- 使用字典中不存在的鍵
- 忘了括號(hào)
- 漏傳參數(shù)
- 缺失依賴庫
- 使用了python中對(duì)關(guān)鍵詞
- 編碼問題
1. 忘記寫冒號(hào)
在 if、elif、else、for、while、def語句后面忘記添加 :age = 42if age == 42 print('Hello!')
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- age = 42
- if age == 42
- print ( 'Hello!' )
- File "
" , line 2 - if age == 42
- ^
- SyntaxError : invalid syntax
2. 誤用 =
= 是賦值操作，而判斷兩個(gè)值是否相等是 ==
- gender = '男'
- if gender = '男' :
- print ( 'Man' )
- File "
" , line 2 - if gender = '男' :
- ^
- SyntaxError : invalid syntax
3. 錯(cuò)誤的縮進(jìn)
Python用縮進(jìn)區(qū)分代碼塊，常見的錯(cuò)誤用法：
- print('Hello!')
- print('Howdy!')
- File "
", line 2 - print('Howdy!')
- ^
- IndentationError: unexpected indent
- num = 25
- if num == 25:
- print('Hello!')
- File "
", line 3 - print('Hello!')
- ^
- IndentationError: expected an indented block
4. 變量沒有定義
- if city in ['New York', 'Bei Jing', 'Tokyo']: print('This is a mega city')
- ---------------------------------------------------------------------------
- NameError Traceback (most recent call last) in
- ----> 1 if city in ['New York', 'Bei Jing', 'Tokyo']:
- 2 print('This is a mega city')
- NameError: name 'city' is not defined
5. 中英文輸入法導(dǎo)致的錯(cuò)誤
- 英文冒號(hào)
- 英文括號(hào)
- 英文逗號(hào)
- 英文單雙引號(hào)
- if 5>3：
- print('5比3大')
- File "
", line 1 - if 5>3：
- ^
- SyntaxError: invalid character in identifier
- if 5>3:
- print('5比3大')
- File "
", line 2 - print('5比3大')
- ^
- SyntaxError: invalid character in identifier
- spam = [1, 2，3]
- File "
", line 1 - spam = [1, 2，3]
- ^
- SyntaxError: invalid character in identifier
- if 5>3:
- print('5比3大‘)
- File "
", line 2 - print('5比3大‘)
- ^
- SyntaxError: EOL while scanning string literal
6. 不同數(shù)據(jù)類型的拼接
字符串/列表/元組 支持拼接
字典/集合不支持拼接
- 'I have ' + 12 + ' eggs.
- '#'I have {} eggs.'.format(12)
- ---------------------------------------------------------------------------
- TypeError Traceback (most recent call last) in
- ----> 1 'I have ' + 12 + ' eggs.'
- TypeError: can only concatenate str (not "int") to str
- ['a', 'b', 'c']+'def'
- ---------------------------------------------------------------------------
- TypeError Traceback (most recent call last) in
- ----> 1 ['a', 'b', 'c']+'def'
- TypeError: can only concatenate list (not "str") to list
- ('a', 'b', 'c')+['a', 'b', 'c']
- ---------------------------------------------------------------------------
- TypeError Traceback (most recent call last) in
- ----> 1 ('a', 'b', 'c')+['a', 'b', 'c']
- TypeError: can only concatenate tuple (not "list") to tuple
- set(['a', 'b', 'c'])+set(['d', 'e'])
- ---------------------------------------------------------------------------
- TypeError Traceback (most recent call last) in
- ----> 1 set(['a', 'b', 'c'])+set(['d', 'e'])
- TypeError: unsupported operand type(s) for +: 'set' and 'set'
- grades1 = {'Mary':99, 'Henry':77}
- grades2 = {'David':88, 'Unique':89}
- grades1+grades2
- ---------------------------------------------------------------------------
- TypeError Traceback (most recent call last) in
- 2 grades2 = {'David':88, 'Unique':89}
- 3
- ----> 4 grades1+grades2
- TypeError: unsupported operand type(s) for +: 'dict' and 'dict'
7. 索引位置問題
- spam = ['cat', 'dog', 'mouse']
- print(spam[5])
- ---------------------------------------------------------------------------
- IndexError Traceback (most recent call last) in
- 1 spam = ['cat', 'dog', 'mouse']
- ----> 2 print(spam[5])
- IndexError: list index out of range
8. 使用字典中不存在的鍵
在字典對(duì)象中訪問 key 可以使用 []，
但是如果該 key 不存在，就會(huì)導(dǎo)致：KeyError: 'zebra'
- spam = {'cat': 'Zophie', 'dog': 'Basil', 'mouse': 'Whiskers'}
- print(spam['zebra'])
- ---------------------------------------------------------------------------
- KeyError Traceback (most recent call last) in
- 3 'mouse': 'Whiskers'}
- 4
- ----> 5 print(spam['zebra'])
- KeyError: 'zebra'
為了避免這種情況，可以使用 get 方法
- spam = {'cat': 'Zophie', 'dog': 'Basil', 'mouse': 'Whiskers'}
- print(spam.get('zebra'))
- None
key 不存在時(shí)，get 默認(rèn)返回 None
9. 忘了括號(hào)
當(dāng)函數(shù)中傳入的是函數(shù)或者方法時(shí)，容易漏寫括號(hào)
- spam = {'cat': 'Zophie', 'dog': 'Basil', 'mouse': 'Whiskers'}
- print(spam.get('zebra')
- File "", line 5
- print(spam.get('zebra')
- ^
- SyntaxError: unexpected EOF while parsing
10. 漏傳參數(shù)
- def diyadd(x, y, z): return x+y+zdiyadd(1, 2)
- ---------------------------------------------------------------------------
- TypeError Traceback (most recent call last) in
- 2 return x+y+z
- 3
- ----> 4 diyadd(1, 2)
- TypeError: diyadd() missing 1 required positional argument: 'z'
11. 缺失依賴庫
電腦中沒有相關(guān)的庫
12. 使用了python中的關(guān)鍵詞
如try、except、def、class、object、None、True、False等
- try = 5print(try)
- File "
", line 1 - try = 5
- ^
- SyntaxError: invalid syntax
- def = 6
- print(6)
- File "
", line 1 - def = 6
- ^
- SyntaxError: invalid syntax
13. 文件編碼問題
- import pandas as pd
- df = pd.read_csv('data/twitter情感分析數(shù)據(jù)集.csv')
- df.head()
嘗試encoding編碼參數(shù)傳入utf-8、gbk
- df = pd.read_csv('data/twitter情感分析數(shù)據(jù)集.csv', encoding='utf-8')
- df.head()
都報(bào)錯(cuò)說明編碼不是utf-8和gbk，而是不常見都編碼，這里我們需要傳入正確都encoding，才能讓程序運(yùn)行。
python有個(gè)chardet庫，專門用來偵測編碼。
- import chardet
- binary_data = open('data/twitter情感分析數(shù)據(jù)集.csv', 'rb').read()
- chardet.detect(binary_data)
- {'encoding': 'Windows-1252', 'confidence': 0.7291192008535122, 'language': ''}
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